Bump jekyll-redirect-from to v0.5.0

Support new `redirect_to` directive. Now automatically prefixes URLs with `site.github.url`, or `site.baseurl`, with that order of precedence.

Release: https://github.com/jekyll/jekyll-redirect-from/releases/tag/v0.5.0
Diff: https://github.com/jekyll/jekyll-redirect-from/compare/v0.4.0...v0.5.0