Update README

See merge request !6

Fix Spanish translation following coding-standards updates

Closes #5

See merge request !5

Numbered placeholders were added, unintentionally invalidating existing
translations.

Fixes #5.

Add bulk actions

Closes #1 and #4

See merge request !4

Fixes #4

Unit tests and coding standards

Closes #2 and #3

See merge request !3

Fixes #3, which was a misdiagnosis.

Add screenshots previously missing from git

See merge request !2

Add automated WP.org deploys

See merge request !1