PLANET-5397 Sync translatable strings to language po files

[planet-4]

When looking at the source code (and the editor) there are a lot of possibly translatable strings. These strings are not present in the .pot language files, so are missing from the strings that people can translate.

Tasks

• Look for translatable strings that are missing from .po files in both app repos and add them.
• Use poedit to generate the .mo files.
• Write a documentation page on how we create .po files.

Screenshots

Reporter: okeur
Sections: Translations

Potentially affected repositories: planet4-master-theme, planet4-plugin-gutenberg-blocks

[comzeradd]

Done in greenpeace/planet4-plugin-gutenberg-blocks#383