enh(lua) add 'pluto' as an alias (#4110)

[Pluto](https://pluto-lang.org/) is a fork of Lua that uses the .pluto extension.

CHANGES.md

@@ -15,6 +15,7 @@ Core Grammars:
 - enh(erlang) OTP25/27 maybe statement [nixxquality][]
 - enh(dart) Support digit-separators in number literals [Sam Rawlins][]
 - enh(csharp) add Contextual keywords `file`, `args`, `dynamic`, `record`, `required` and `scoped` [Alvin Joy][]
+- enh(lua) add 'pluto' as an alias [Sainan]
 - enh(bash) add reserved keywords `time` and `coproc` [Álvaro Mondéjar][]
 - fix(c) - Fixed hex numbers with decimals  [Dxuian]
 - fix(ruby) - fix `|=` operator false positives (as block arguments) [Aboobacker MK]
@@ -47,6 +48,7 @@ CONTRIBUTORS
 [Dxuian]:https://github.com/Dxuian
 [Aboobacker MK]: https://github.com/tachyons
 [Imken]: https://github.com/immccn123
+[Sainan]: https://github.com/Sainan
 [Osmocom]: https://github.com/osmocom
 [Álvaro Mondéjar]: https://github.com/mondeja
 

SUPPORTED_LANGUAGES.md

@@ -130,7 +130,7 @@ The table below shows the full list of languages (and corresponding classes/alia
 | LiveCode Server         | livecodeserver         |         |
 | LiveScript              | livescript, ls         |         |
 | LookML                  | lookml                 | [highlightjs-lookml](https://github.com/spectacles-ci/highlightjs-lookml) |
-| Lua                     | lua                    |         |
+| Lua                     | lua, pluto             |         |
 | Luau                    | luau                   | [highlightjs-luau](https://github.com/highlightjs/highlightjs-luau) |
 | Macaulay2               | macaulay2              | [highlightjs-macaulay2](https://github.com/d-torrance/highlightjs-macaulay2) |
 | Makefile                | makefile, mk, mak, make |        |

src/languages/lua.js

@@ -27,6 +27,7 @@ export default function(hljs) {
   ];
   return {
     name: 'Lua',
+    aliases: ['pluto'],
     keywords: {
       $pattern: hljs.UNDERSCORE_IDENT_RE,
       literal: "true false nil",