Is your feature request related to a problem? Please describe.

Per the discussion in #2073 (comment), we should add an alternative to passing a post slug or title to Timber::get_post(), because that won’t be supported anymore in Timber 2.0.

Describe the solution you’d like

• Add Timber::get_post_by_slug().
• Add Timber::get_post_by_title().
• Update Upgrade Guide.

Describe alternatives you’ve considered

See #2073 (comment).