Adds bundle size measurement and reporting for the @fluentui/react-icons package, integrating the monosize tool into the workflow and adding supporting configuration.

1. new PR workflow step

• runs monosize measure for existing fixtures
• runs monosize compare-reports comparing repo stored storage vs current PR measurement

1. adds "dummy" createLocalStorage which operates on physical repo files

• stores baseline via default branch main pipeline to repo
  • NOTE: this might not work (depends on repo setup of protected branches) and will need to be reworked to use GHA artifacts