Add cmake file rules to .editorconfig

Author: mhucka

.editorconfig

@@ -38,6 +38,9 @@ max_line_length = 80
 [{BUILD,*.BUILD,*.bzl,*.bazel,.bazelrc}]
 indent_size = 4
 
+[{CMakeLists.txt,*.cmake}]
+indent_size = 4
+
 [{*.cc,*.h}]
 indent_size = 2