Ability to put MSC goal progress in room topic

Add a new command like:

```
set topic goal Bla bla bla this is my topic. r0 progress: $progress$.
```

And `$progress$` would be replaced by `5/7` for example.

Whenever setting a summary (and this is required), the bot would update the topic.

Start at the bot's command handling for `set topic goal` and the existing summary-setting flow. Trace how MSC progress is calculated and how room topics are updated. Done means the command accepts `$progress$`, replaces it with a value such as `5/7`, and updates the topic whenever a summary is set.

Written by the indexing model from the issue text.