message: Add \addplot grammar support
  The content of the command \addplot is considered as gnuplot code.
  Note that the closing '};' must be on a line of its own.
  Related to
diff: ],
  "end": "(\\\\end\\{gnuplot\\}(?:\\s*\\n)?)"
  },
  + {
  + "begin": "((\\\\)addplot)(?:\\+?)((?:\\[[^\\[]*\\]))*\\s*(gnuplot)\\s*((?:\\[[^\\[]*\\]))*\\s*(\\{)",
  + "captures": {
  + "1": {
  + "name": "support.function.be.latex"
  + },
  + "2": {
  + "name": "punctuation.definition.function.latex"
  + },
  + "3": {
  + "patterns": [
  + {
  + "include": "#optional-arg"
  + }
  + ]
  + },
  + "4": {
  + "name": "variable.parameter.function.latex"
  + },
  + "5": {
  + "patterns": [
  + {
  + "include": "#optional-arg"
  + }
  + ]
  + },
  + "6": {
  + "name": "punctuation.definition.arguments.begin.latex"
  + }
  + },
  + "contentName": "source.gnuplot",
  + "patterns": [
  + {
  + "include": "source.gnuplot"
  + }
  + ],
  + "end": "\\s*(\\};)"
  + },
  {
  "begin": "(?:\\s*)((\\\\)begin)(\\{)((?:fboxv|boxedv|V|v)erbatim\\*?)(\\})",
  "captures": {
  },
  "end": "((\\\\)end)(\\{)(\\4)(\\})(?:\\s*\\n)?",
  "name": "meta.function.environment.latex.mpost"
  - },{
  + },
  + {
  "begin": "(?:\\s*)((\\\\)begin)(\\{)(\\w+[*]?)(\\})",
  "captures": {
  "1": {
  