Add /.cpplsp.buckd to react-native-github/.gitignore

Summary:
Something keeps creating these cpp lsp files in react-native-github, which is annoying.
{F1056848131}
This diff adds `.gitignore` section to ignore them.
Changelog: [Internal] - Add /.cpplsp.buckd to react-native-github/.gitignore

bypass-github-export-checks

Reviewed By: cortinico, cipolleschi

Differential Revision: D47716855

fbshipit-source-id: 78d2008f69c230d746546afad80c9114d27c9026

.gitignore

@@ -52,6 +52,7 @@ buck-out
 /.lsp-buck-out
 /packages/react-native/ReactAndroid/src/main/jni/prebuilt/lib/
 /packages/react-native/ReactAndroid/src/main/gen
+/.cpplsp.buckd
 
 # Android Studio
 .project