Add hightlight groups for nvim-treesitter (#230)

* Add hightlight groups for nvim-treesitter

The majority of this configuration was taken from
https://github.com/ChristianChiarulli/nvcode-color-schemes.vim/pull/14
by [@nitishvelu](https://github.com/nitishvelu). I made a few minor
tweaks based on a ruby project to make sure most of the original tokens
were colored similarly.

* tree-sitter highlights conform to dracula spec

* Use builtin highlight groups

Co-authored-by: Derek Sifford <dereksifford@gmail.com>

* Apply suggestions from code review

Co-authored-by: Derek Sifford <dereksifford@gmail.com>

Co-authored-by: Derek Sifford <dereksifford@gmail.com>

after/plugin/dracula.vim

@@ -41,5 +41,66 @@ if exists('g:loaded_ctrlp')
   hi! link CtrlPBufferHid Normal
 endif
 " }}}
+" Tree-sitter: {{{
+if exists('g:loaded_nvim_treesitter')
+  " # Misc
+  hi! link TSError ErrorMsg
+  hi! link TSPunctDelimiter Delimiter
+  hi! link TSPunctBracket Normal
+  hi! link TSPunctSpecial Special
+  " # Constants
+  hi! link TSConstant Constant
+  hi! link TSConstBuiltin Constant
+  hi! link TSConstMacro Macro
+  hi! link TSStringRegex String
+  hi! link TSString String
+  hi! link TSStringEscape Character
+  hi! link TSSymbol DraculaPurple
+  hi! link TSCharacter Character
+  hi! link TSNumber Number
+  hi! link TSBoolean Boolean
+  hi! link TSFloat Float
+  hi! link TSAnnotation DraculaYellow
+  hi! link TSAttribute DraculaGreenItalic
+  hi! link TSNamespace Structure
+  " # Functions
+  hi! link TSFuncBuiltin DraculaCyan
+  hi! link TSFunction Function
+  hi! link TSFuncMacro Function
+  hi! link TSParameter DraculaOrangeItalic
+  hi! link TSParameterReference DraculaOrange
+  hi! link TSMethod Function
+  hi! link TSField DraculaOrange
+  hi! link TSProperty Normal
+  hi! link TSConstructor DraculaCyan
+  " # Keywords
+  hi! link TSConditional Conditional
+  hi! link TSRepeat DraculaPink
+  hi! link TSLabel DraculaPurpleItalic
+  hi! link TSKeyword Keyword
+  hi! link TSKeywordFunction DraculaCyan
+  hi! link TSKeywordOperator Operator
+  hi! link TSOperator Operator
+  hi! link TSException DraculaPurple
+  hi! link TSType Type
+  hi! link TSTypeBuiltin Type
+  hi! link TSStructure Structure
+  hi! link TSInclude Include
+  " # Variable
+  hi! link TSVariable Normal
+  hi! link TSVariableBuiltin DraculaPurpleItalic
+  " # Text
+  hi! link TSText Normal
+  hi! link TSStrong DraculaFgBold
+  hi! link TSEmphasis DraculaFg
+  hi! link TSUnderline Underlined
+  hi! link TSTitle DraculaYellow
+  hi! link TSLiteral DraculaYellow
+  hi! link TSURI DraculaYellow
+  " # Tags
+  hi! link TSTag DraculaCyan
+  hi! link TSTagDelimiter Normal
+endif
+" }}}
 
 " vim: fdm=marker ts=2 sts=2 sw=2 fdl=0: