Add prettier config file.

Author: infokiller

.prettierrc.yml

@@ -0,0 +1,11 @@
+# For a list of available options see https://prettier.io/docs/en/options.html
+
+# Options not set in this file should have defaults that already match Google's
+# style from: # https://github.com/google/ts-style
+
+# Note that prettier reads indentation size and type (tabs/spaces) from
+# editorconfig if it finds an editorconfig file, so these settings should only
+# be set on the editorconfig file to preserve consistency. See also:
+# https://github.com/prettier/prettier/issues/42#issuecomment-327073326
+
+singleQuote: true