doc: add c tips

Author: HerringtonDarkholme

website/catalog/c/index.md

@@ -2,6 +2,10 @@
 
 This page curates a list of example ast-grep rules to check and to rewrite C code.
 
+:::tip C files can be parsed as Cpp
+You can parse C code as Cpp to avoid rewriting similar rules. The [`languageGlobs`](/reference/sgconfig.html#languageglobs) option can force ast-grep to parse `.c` files as Cpp.
+:::
+
 <!--@include: ./match-function-call.md-->
 <!--@include: ./rewrite-method-to-function-call.md-->
 <!--@include: ./yoda-condition.md-->

website/catalog/cpp/index.md

@@ -0,0 +1,7 @@
+# Cpp
+
+This page curates a list of example ast-grep rules to check and to rewrite Cpp code.
+
+:::tip Reuse Cpp rules with C
+Cpp is a superset of C, so you can reuse Cpp rules with C code. The [`languageGlobs`](/reference/sgconfig.html#languageglobs) option can force ast-grep to parse `.c` files as Cpp.
+:::