Link to Discord and Slack more obviously

[phillco]

The communities are pretty helpful for getting started! We should probably link them on:

• [ ] Wherever "getting started" on the homepage lands to, which is currently https://www.cursorless.org/docs/
• [ ] Persistently in the footer, the way Sapling does (I personally would not have realized they had a community, had they not done this)

It might also be good to mention the regular meetups on the "getting started" page too, probably by linking to the Talon events calendar the way we do in Slack.