chore(repo): Update links in all READMEs

[LekoArts]

Description

Follow up to #1709 - The old templates were referenced in the READMEs so the links needed an update.

I also did:

• Change the Discord link to our clerk.com/discord shortlink so that if in the future the invite expires or somehow doesn't work, we don't need to publish a new version to update the link in the READMEs
• Our main README uses a light/dark version of the logo depending on the system status. I've updated each README to also use that pattern instead of always the light version
• I removed two images from the docs folder since they were unused
• Linked our GitHub discussion for people to ask questions

Checklist

• npm test runs as expected.
• npm run build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

Packages affected

• all packages

[changeset-bot]

🦋 Changeset detected

Latest commit: 4dcb4b8

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 13 packages

Name	Type
gatsby-plugin-clerk	Patch
@clerk/chrome-extension	Patch
@clerk/localizations	Patch
@clerk/clerk-js	Patch
@clerk/clerk-sdk-node	Patch
@clerk/backend	Patch
@clerk/fastify	Patch
@clerk/nextjs	Patch
@clerk/themes	Patch
@clerk/clerk-react	Patch
@clerk/remix	Patch
@clerk/types	Patch
@clerk/clerk-expo	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[anagstef]

Nice one!