Add indentation rules for GLSL syntax (#58520)

Add C-Style indentation rules for GLSL. By adding an indents.scm file
for GLSL we get the same automatic indentation as we have for other
languages.

Release Notes:

- N/A

extensions/glsl/languages/glsl/indents.scm

@@ -0,0 +1,30 @@
+[
+  (field_expression)
+  (assignment_expression)
+  (init_declarator)
+  (if_statement)
+  (for_statement)
+  (while_statement)
+  (do_statement)
+  (else_clause)
+] @indent
+
+(_
+  "{"
+  "}" @end) @indent
+
+(_
+  "("
+  ")" @end) @indent
+
+(if_statement) @start.if
+
+(for_statement) @start.for
+
+(while_statement) @start.while
+
+(do_statement) @start.do
+
+(switch_statement) @start.switch
+
+(else_clause) @start.else