chore(git): Add clangd generated files to .gitignore (#9073)

Co-authored-by: Artyom Ivanov <artyom.ivanov@red-soft.ru>

Author: TreeHunter9

.gitignore

@@ -29,4 +29,9 @@ extern/ttmath/release/
 /src/include/gen/autoconfig.auto
 /src/include/gen/autoconfig.h
 /vcpkg_installed/
-.idea/
+.idea/
+
+# clangd index and background cache
+/.cache/clangd
+# Compilation database generated for clangd
+/compile_commands.json