Add "Gym" as keyword for working out illustrations

[rspencer01]

This commit adds "Gym" as a word to show working out illustrations,
as well as adds translations to Afrikaans and Esperanto.

Description

Adds a word to match to working out events.
Fixes #1888

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I signed off my changes (git commit -sm "Your commit message")
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[georgehrke]

@rspencer01 Can you please remove the translation changes and sign off you commits?

Our translations are managed on https://transifex.com. The translation changes you did here will just be overridden next night when the translation bot updates our translations.

[georgehrke]

Thx for your contribution!