Add 3rd party CODEOWNERS grammar to SUPPORTED_LANGUAGES.md (highlightjs#3919)

Co-authored-by: Nataliia Radina <nradina@gitlab.com>

Author: Nataliia-Radina

CHANGES.md

@@ -7,6 +7,10 @@ Core Grammars:
 - fix(yaml) fix for yaml with keys having brackets highlighted incorrectly [Aneesh Kulkarni][]
 - fix(bash) fix # within token being detected as the start of a comment [Felix Uhl][]
 
+New Grammars:
+
+- added 3rd party CODEOWNERS grammar to SUPPORTED_LANGUAGES [nataliia-radina][]
+
 Developer Tool:
 
 - enh(tools): order CSS options picklist [David Schach][]
@@ -16,6 +20,7 @@ Developer Tool:
 [Aneesh Kulkarni]: https://github.com/aneesh98
 [Bruno Meneguele]: https://github.com/bmeneg
 [Felix Uhl]: https://github.com/iFreilicht
+[nataliia-radina]: https://github.com/Nataliia-Radina
 
 
 ## Version 11.9.0

SUPPORTED_LANGUAGES.md

@@ -45,7 +45,8 @@ The table below shows the full list of languages (and corresponding classes/alia
 | Cache Object Script     | cos, cls               |         |
 | Candid                  | candid, did            | [highlightjs-motoko](https://github.com/rvanasa/highlightjs-motoko) |
 | CMake                   | cmake, cmake.in        |         |
-| COBOL                   | cobol, standard-cobol   | [highlightjs-cobol](https://github.com/otterkit/highlightjs-cobol) |
+| COBOL                   | cobol, standard-cobol  | [highlightjs-cobol](https://github.com/otterkit/highlightjs-cobol) |
+| CODEOWNERS              | codeowners             | [highlightjs-codeowners](https://github.com/highlightjs/highlightjs-codeowners) |
 | Coq                     | coq                    |         |
 | CSP                     | csp                    |         |
 | CSS                     | css                    |         |