feat: add few more block types & improve their availability
- Add CardBlock to provide generic card
- Add FigureBlock to provide generic figure embed
- Add TwoColumnBlock & ThreeColumnBlock to support multicolumn content editing
- Add ButtonBlock & ButtonGroup block to embed buttons
- Add ImageBannerBlock to enable embedding image banners
- Allow more blocks to be used in district pages & unify which specifically
Election templates were intentionally left out as they will be subject of a following MR.
Edited by filip.varecha