Add .clangd to .gitignore

No-Try: true
Change-Id: I9c4d6f02451872dacf6e5e172ec32afde5f80281
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1943165
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65270}

.gitignore

@@ -24,6 +24,7 @@
 .#*
 .*.sw?
 .ccls-cache
+.clangd
 .cpplint-cache
 .cproject
 .gclient_entries