[clangd] Allow *.h file as c++ header (#128)

Author: tgtakaoka

.clangd

@@ -0,0 +1,18 @@
+# -*- mode: yaml; mode: flyspell-prog; -*-
+
+If:
+  PathMatch: .*\.h
+  CompileFlags:
+    Add: [-xc++]
+
+CompileFlags:
+  Add:
+    - -Idebugger
+
+Diagnostics:
+  ClangTidy:
+    Remove:
+      # suppress ExtendedClass::parentClassMethod
+      - readability-qualified-auto
+
+