153: integrate mini dashboard r=MarinPostma a=MarinPostma
This PR integrate the [mini dashboard](https://github.com/meilisearch/mini-dashboard) to transplant.
It adds a build feature `mini-dashboard` to statically add the mini-dashboard to the MeiliSearch binary. The mini-dashboard build feature is enabled by default and can be disabled by building MeiliSearch with `cargo build --no-default-features`.
- [x] Fetch the mini-dashboard from the Github release
- [x] Check that the SHA1 on the downloaded payload matches the one in the metadata
- [x] Unpack the mini dashboard in `meilisearch-http/mini-dashboard`
- [x] serve the mini-dashboard if the `mini-dashboard` feature is enabled
- [x] Update CI to build MeiliSearch with mini-dashboard for releases
close#87
## Shasum check and build optimizations.
In order to make sure that the right bundle for the mini-dashboard is downloaded, its shasum is computed and compared to the one specified in the `Cargo.toml`. If the shasums match, them the shasum is written to the `.mini-dashboard.sha1` file for later comparison. On subsequent builds, the build script will check that both the mini-dashboard assets and the shasum file are found and that the shasum file content matches the one from the toml file. It will only preform a re-generation on the static dashboard files if it finds that either the dashboard is not present where it expects it to be, or if it finds out that it is outdated, by comparing the shasums.
## Notes
I had to rely on a [custom patch](https://github.com/MarinPostma/actix-web-static-files/tree/actix-web-4) of actix-web-static-files, to support actix-web 4 beta6. there is currently a [pr on the official repo](https://github.com/kilork/actix-web-static-files/pull/35) to support actix-web 4, but it most likely won't be merged until actix is stabilized.
Co-authored-by: Marin Postma <postma.marin@protonmail.com>
