Add instructions for registering IRC bot's nickname

[DylanVanAssche]

Setting up your own Matrix IRC bridge might require that you register the nickname of your IRC bot.
Some channels won't allow your bot to join without a registered nickname. As a result, the bot won't be able to join and cannot bridge the channel to Matrix.

This feature is already supported by the bridge, however it was not mentioned in the HOWTO.md guide for rolling your own bridge.

Signed-off-by: Dylan Van Assche dylan.van.assche@protonmail.com

[Half-Shot]

This seems good to me. Thanks 👍

[Half-Shot]

Oh, almost! Can you base your changes against develop please?

[DylanVanAssche]

Changes based against develop 🚀

[Half-Shot]

Oh and final final thing, as per https://github.com/matrix-org/matrix-appservice-irc/blob/master/CONTRIBUTING.md#making-pull-requests, could you add a changelog file so we can keep track of changes.

Create a changelog entry in changelog.d. A changelog filename should be ${GithubIssueNumber}.{bugfix|misc|feature|doc|removal} The change should include information that is useful to the user rather than the developer.

Rememver to stick your github handle on the end of the changelog file to get credited :)

[DylanVanAssche]

I don't have a Github Issue, do I need one first? That's also the reason why I skipped the changelog thing when creating this PR

[Half-Shot]

Ah, the issue number is this PR's number (1004). Probably not clear enough in the docs.

[DylanVanAssche]

Done!

[DylanVanAssche]

Maybe describe in the guidelines the best 'template' for the changelog entries?