Use standard injection.language and injection.content captures (#22268)

Closes #9656. Continuation of #9654, but with the addition of backwards
compatibility for the existing captures.

Release Notes:

- Improved Tree-sitter support with added compatibility for standard
injections captures

---------

Co-authored-by: Finn Evers <finn.evers@outlook.de>

extensions/html/languages/html/injections.scm

@@ -1,7 +1,7 @@
 (script_element
-  (raw_text) @content
-  (#set! "language" "javascript"))
+  (raw_text) @injection.content
+  (#set! injection.language "javascript"))
 
 (style_element
-  (raw_text) @content
-  (#set! "language" "css"))
+  (raw_text) @injection.content
+  (#set! injection.language "css"))