Add Markdown plugin plasticboy/vim-markdown

The "plasticboy/vim-markdown" (1) extends the syntax highlighting support
and provides additional features compared to the default syntax
definitions.

References:
  (1) https://github.com/plasticboy/vim-markdown

GH-38

snowblocks/vim/vimrc

@@ -15,23 +15,29 @@
 "+ Plugins +
 "+---------+
 call plug#begin(expand('~/.vim/plugged'))
+"+--- IDE / Workflow ---+
 Plug 'mattn/emmet-vim'
-Plug 'Yggdroot/indentLine'
 Plug 'davidhalter/jedi-vim'
+Plug 'Townk/vim-autoclose'
+Plug 'tpope/vim-fugitive'
+if v:version >= 704
+  Plug 'honza/vim-snippets'
+  Plug 'SirVer/ultisnips'
+endif
+
+"+--- UI ---+
+Plug 'Yggdroot/indentLine'
 Plug 'itchyny/lightline.vim'
 Plug 'scrooloose/nerdtree'
-Plug 'Townk/vim-autoclose'
 Plug 'gorodinskiy/vim-coloresque'
-Plug 'tpope/vim-fugitive'
 Plug 'airblade/vim-gitgutter'
+
+"+--- Syntax ---+
 Plug 'pangloss/vim-javascript'
+Plug 'plasticboy/vim-markdown'
 
+"+--- Color Themes ---+
 Plug 'arcticicestudio/nord-vim'
-
-if v:version >= 704
-  Plug 'honza/vim-snippets'
-  Plug 'SirVer/ultisnips'
-endif
 call plug#end()
 
 "+--- Yggdroot/indentLine ---+