docs: add READMEs to each modules' directory (#10721)

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## Description

Closes: #10588

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---

### Author Checklist

*All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow up issues.*

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/master/docs/building-modules)
- [x] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/master/CONTRIBUTING.md#testing)
- [ ] added a changelog entry to `CHANGELOG.md`
- [ ] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [ ] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

x/README.md

@@ -6,12 +6,13 @@ order: 0
 
 Here are some production-grade modules that can be used in Cosmos SDK applications, along with their respective documentation:
 
-- [Auth](auth/spec/README.md) - Authentication of accounts and transactions for Cosmos SDK application.
+- [Auth](auth/spec/README.md) - Authentication of accounts and transactions for Cosmos SDK applications.
 - [Authz](authz/spec/README.md) - Authorization for accounts to perform actions on behalf of other accounts.
 - [Bank](bank/spec/README.md) - Token transfer functionalities.
 - [Capability](capability/spec/README.md) - Object capability implementation.
 - [Crisis](crisis/spec/README.md) - Halting the blockchain under certain circumstances (e.g. if an invariant is broken).
 - [Distribution](distribution/spec/README.md) - Fee distribution, and staking token provision distribution.
+- [Epoching](epoching/spec/README.md) - Allows modules to queue messages for execution at a certain block height.
 - [Evidence](evidence/spec/README.md) - Evidence handling for double signing, misbehaviour, etc.
 - [Feegrant](feegrant/spec/README.md) - Grant fee allowances for executing transactions.
 - [Governance](gov/spec/README.md) - On-chain proposals and voting.

x/auth/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Auth
+
+- [Auth](spec/README.md) - Authentication of accounts and transactions for Cosmos SDK applications.

x/authz/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Authz
+
+- [Authz](spec/README.md) - Authorization for accounts to perform actions on behalf of other accounts.

x/bank/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Bank
+
+- [Bank](spec/README.md) - Token transfer functionalities.

x/capability/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Capability
+
+- [Capability](spec/README.md) - Object capability implementation.

x/crisis/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Crisis
+
+- [Crisis](spec/README.md) - Halting the blockchain under certain circumstances (e.g. if an invariant is broken).

x/distribution/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Distribution
+
+- [Distribution](spec/README.md) - Fee distribution, and staking token provision distribution.

x/epoching/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Epoching
+
+- [Epoching](epoching/spec/README.md) - Allows modules to queue messages for execution at a certain block height.

x/evidence/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Evidence
+
+- [Evidence](spec/README.md) - Evidence handling for double signing, misbehaviour, etc.

x/feegrant/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Feegrant
+
+- [Feegrant](spec/README.md) - Grant fee allowances for executing transactions.

x/gov/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Governance
+
+- [Governance](spec/README.md) - On-chain proposals and voting.

x/mint/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Mint
+
+- [Mint](spec/README.md) - Creation of new units of staking token.

x/params/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Params
+
+- [Params](spec/README.md) - Globally available parameter store.

x/slashing/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Slashing
+
+- [Slashing](spec/readme.md) - validator punishment mechanisms.

x/staking/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Staking
+
+- [Staking](spec/README.md) - Proof-of-Stake layer for public blockchains.

x/upgrade/README.md

@@ -0,0 +1,7 @@
+<!--
+order: 0
+-->
+
+# Upgrade
+
+- [Upgrade](spec/README.md) - Software upgrades handling and coordination.