Dynamically locate bootswatch directory, mount to /_theme

The previous implementation using symlinks does not work on npm
(which doesn't allow symlinks)

src/app.js

@@ -1,3 +1,4 @@
+import path from 'path'
 import { pwrap, pick, fcurrency, fmsat, pngPixel } from './lib/util'
 
 // Setup
@@ -40,6 +41,7 @@ app.use(require('csurf')({ cookie: true }))
 // Static assets
 app.use('/_assets', require('stylus').middleware({ src: conf.static_dir, serve: true }))
 app.use('/_assets', require('express').static(conf.static_dir))
+app.use('/_themes', require('express').static(path.resolve(require.resolve('bootswatch/package'), '..', 'dist')))
 
 // Create invoice
 app.post('/_invoice', pwrap(async (req, res) => {

static/bootswatch

@@ -1 +0,0 @@
-../node_modules/bootswatch/dist

views/layout.pug

@@ -10,7 +10,7 @@ block head
 
   title= title
 
-  link(rel='stylesheet', href='_assets/bootswatch/'+conf.theme+'/bootstrap.min.css')
+  link(rel='stylesheet', href='_themes/'+conf.theme+'/bootstrap.min.css')
   link(rel='stylesheet', href='_assets/style.css')
   noscript: style .yesscript{display:none}