PLAT-631 Update campaign buttons

[Heleen-cr]

Fixes https://jira.comicrelief.com/browse/PLAT-631

Changes proposed in this pull request

• add black and white ghost buttons to the styles dropdown in wysiwyg editor
• change all buttons to be the small version when used in content wall and big if used anywhere else

Manual config:

editor.editor.basic_html.yml
editor.editor.full_html.yml
need to be updated in the RND profile.

[gusliedke]

@Heleen-cr small version is the ghost btn style (padding/font size). All btns within cw should be the same size of ghost btn (small btn). Now can you ask jeff if ghost btn outside content wall has same size of other btns?

[gusliedke]

Jeff has confirmed .. ghost button outside cw has same size of other btns.