Vim: Fix vim config and update docs (#24)

There was a refactor (9613807) that moved the vim theme from
`light/Vim/colors` to `themes/Vim`.  This created two problems:
1. Vim expects themes to be under the `/colors` directory
2. The docs weren't updated to reflect the new plugin directory

light/Readme.md

@@ -17,6 +17,7 @@
 - [Slack](../themes/Slack)
 - [Sublime Text](../themes/Sublime%20Text)
 - [Telegram](../themes/Telegram)
+- [Vim](../themes/Vim)
 - [Visual Studio Code](../themes/VSCode)
 - [Vivaldi](../themes/Vivaldi)
 

themes/Vim/Readme.md

@@ -14,27 +14,27 @@ Set `g:squirrelsong_color_only` to `v:true` beforehand to disable additional sty
 {
   "sapegin/squirrelsong",
   config = function(plugin)
-    vim.opt.rtp:append(plugin.dir .. "/light/Vim")
+    vim.opt.rtp:append(plugin.dir .. "/themes/Vim")
   end,
 }
 ```
 
 ## Installation with [packer.nvim](https://github.com/wbthomason/packer.nvim)
 
 ```lua
-use { 'sapegin/squirrelsong', rtp = 'light/Vim' }
+use { 'sapegin/squirrelsong', rtp = 'themes/Vim' }
 ```
 
 ## Installation with [vim-plug](https://github.com/junegunn/vim-plug)
 
 ```vim
 call plug#begin()
   ...
-  Plug 'sapegin/squirrelsong', { 'rtp': 'light/Vim' }
+  Plug 'sapegin/squirrelsong', { 'rtp': 'themes/Vim' }
   ...
 call plug#end()
 ```
 
 ## Installation from GitHub
 
-Put [`squirrelsong_light.vim`](squirrelsong_light.vim) in the `colors` directory somewhere on your `'rtp'`. `:echo &rtp` will print your `'rtp'`.
+Put [`squirrelsong_light.vim`](colors/squirrelsong_light.vim) in the `colors` directory somewhere on your `'rtp'`. `:echo &rtp` will print your `'rtp'`.