UI: Add Whats New for macOS/Linux

- Requires MbedTLS on Linux
- Enabled by default on macOS and Flatpak
- Enabled on linux via ENABLE_WHATSNEW_LINUX
- Enables compilation of blake2 on Linux/macOS
- Makes header name check also work with lowercase header
- Changes WahtsNew to be only enabled when browser panels are available
This commit is contained in:
Internal Server Error - Gitea: Git with a cup of tea
500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f