Document/automate release process

Currently running the following command to release:

```sh
lerna publish --exact --force-publish=* --repo-version 1.0.0-beta.1
```

- `--exact` since the platforms should have an exact dependency on `@fanny-pack/core`, so that libraries can have `peerDependencies` on a core version and know that the installed platform will fulfill that.
- `--force-publish=*` so that all packages always are at the same version, even if one of the packages didn't have any changes.
- `--repo-version` for specifying the version to bump to

Things that would be nice to fix:

- [ ] Specify the `--exact` flag in `lerna.json`
- [ ] Specify the `--force-publish=*` flag in `lerna.json`
- [ ] Teach Lerna about [emoji-commit](https://github.com/LinusU/emoji-commit), so that the version can be specified automatically

Start with the release command in the issue and inspect lerna.json to determine how --exact and --force-publish=* can be configured. Then investigate the linked emoji-commit tool and Lerna's versioning flow. Done means the release process no longer needs those repeated flags and can derive the repository version automatically.

Written by the indexing model from the issue text.