Add a .clang-tidy file

We currently don't use it for anything. We could add a CI pass in the
future.

We don't enable clang-analyzer checks. The checks enabled here should
mostly be syntax/style linting only, and should be cheap to run.
clang-analyzer checks are usually compute-intensive, and can easily be run
separately anyway, with scan-build and such.

The list of checks definitely isn't final.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

.clang-tidy

@@ -0,0 +1,16 @@
+Checks: >
+  readability-*,
+  performance-*,
+  modernize-*,
+  google-readability-todo,
+  cert-err34-c,
+  cert-flp30-c,
+  bugprone-*,
+  misc-misplaced-const,
+  misc-redundant-expression,
+  misc-static-assert,
+  -clang-analyzer-*,
+  -readability-isolate-declaration,
+  -readability-magic-numbers
+AnalyzeTemporaryDtors: false
+FormatStyle:     file