Remake of the posts creation modal

Working closely with my designers, we have remade the creation model:

• No significant changes to the logic to keep in line with what people love
• Big improvement to the UX
• Big improvement to the UI

This is part 1 of 2 of the migration.
The next version will include previews for multiple social networks.

What's Changed

• fix(ci): Force fresh base image in Docker builds by @adambkovacs in #1118

New Contributors

• @adambkovacs made their first contribution in #1118

Full Changelog: v2.10.1...v2.11.0