liquid 5.7.0 on Ruby Gems

What's Changed

Add find, find_index, has, and reject filters to arrays by @karreiro in #1869
Add the "Releasing" section to CONTRIBUTING.md by @karreiro in #1891
Implement logic for stringify Hashes to keep compat with 3.4 by @ianks in #1892
Allow for custom < Hash classes to override #to_s by @ianks in #1896
Use Liquid::Utils.to_s for join filter by @ianks in #1897
Ensure we use InputIterator#each when in join filter by @ianks in #1898
Bump to 5.7.0 by @karreiro in #1894

Full Changelog: v5.6.4...v5.7.0