Add file associations for "vimrc"

The `vimrc` (1) of Vim (2) was not detected as Vim script syntax,
therefore a association has been added to map it to the `viml` syntax
type provided by the vscode-viml-syntax (3) extension that was added
in GH-184.

References:
  (1) http://vimdoc.sourceforge.net/htmldoc/starting.html#vimrc
  (2) https://www.vim.org
  (3) https://marketplace.visualstudio.com/items?itemName=dunstontc.viml

Resolves GH-191

snowblocks/visual-studio-code/settings.json

@@ -33,9 +33,10 @@
   "extensions.ignoreRecommendations": true,
   "extensions.showRecommendationsOnlyOnDemand": true,
   "files.associations": {
-    "Brewfile": "ruby",
+    "*.js": "javascript",
     "*.jsx": "javascriptreact",
-    "*.js": "javascript"
+    "Brewfile": "ruby",
+    "vimrc": "viml"
   },
   "files.eol": "\n",
   "files.insertFinalNewline": true,