Improve declaration formatting linter rule for anonymous functions
Summary: Ref T8742. Anonymous functions should have a space after the function keyword. Additionally, ensure that there is a space before and after the use token.
Test Plan: Modified existing test cases.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin
Maniphest Tasks: T8742
Differential Revision: https://secure.phabricator.com/D13804