chore: add CodeQL.yml (#232)

This PR adds a CodeQL.yml file to the repository to clearly indicate to
CodeQL which files to exclude.

Author: rzhao271

CodeQL.yml

@@ -0,0 +1,16 @@
+path_classifiers:
+  test:
+    # Note: use only forward slash / as a path separator.
+    # *  Matches any sequence of characters except a forward slash.
+    # ** Matches any sequence of characters, including a forward slash.
+    # This wildcard must either be surrounded by forward slash symbols, or used as the first segment of a path.
+    # It matches zero or more whole directory segments. There is no need to use a wildcard at the end of a directory path because all sub-directories are automatically matched.
+    # That is, /anything/ matches the anything directory and all its subdirectories.
+    # Always enclose the expression in double quotes if it includes *.
+    - "**/tests/**"
+
+  # The default behavior is to tag all files created during the
+  # build as `generated`. Results are hidden for generated code. You can tag
+  # further files as being generated by adding them to the `generated` section.
+  generated:
+    - target