Update .gitignore for clangd

MForster · MForster · commit d96252476cf3 · 2020-08-14T10:15:18.000+02:00
The clangd cache is now stored in a .cache directory (https://reviews.llvm.org/D78501).
diff --git a/.gitignore b/.gitignore
@@ -54,3 +54,4 @@ autoconf/autom4te.cache
 .vs
 # clangd index
 .clangd
+.cache

-Original file line number
+Diff line change
 .vs
 # clangd index
 .clangd
 +.cache