Add deprecation information

[RichieAHB]

Add the deprecation information to the README and link to Leaving Scribe. I will also prefix the GitHub description with DEPRECATED: once this is merged.

Any comments welcome 👍

[RichieAHB]

Also I'm not sure what happened to html-janitor I think we recovered it after having deleted it but it's failing the build as we maybe didn't recover it to the version it was at before deletion (notable 2.0.4). I can either downgrade Scribe back to 2.0.2 but I feel like the patch versions in 2.0.4 probably fixed something worth fixing!

[mbarton]

@RichieAHB I published 2.0.4 a while back to fix some vulnerabilities: guardian/html-janitor#1

It shows as the latest version on npm (https://www.npmjs.com/package/html-janitor). It was 2.0.2 before deletion from memory, with 2.0.4 being my version I released after deleting the repo.

[RichieAHB]

@mbarton ah interesting - the package.json shows as 2.0.4 so it's probably just that some tags got deleted - happy to push 2.0.4 to master.

[mbarton]

Sounds good. Also ewwww github dependencies