Adapt sent over css variables to new color palette

[juliushaertl]

Thanks to the great initiative on standardising the color palette we should be able to adapt more easily by sending over proper values for https://github.com/CollaboraOnline/online/blob/master/browser/css/color-palette.css with the integration.

Ref https://github.com/CollaboraOnline/online/pull/4245#issuecomment-1046772188

[Andreas-Kainz]

There are the following sections

• text
• background
• border

and for each section there is

• main
• dark (for select mode)
• darker (for hover mode)
• lighter (for deactivated)

there is background and color, cause so the user can choose to have border, or not (use the same color than background).

[juliushaertl]

@pedropintosilva This might also one something worth to update on https://sdk.collaboraonline.com/docs/theming.html#content-of-hidden-field-css-variables