Initial setup for Amsterdam theme

[johnbarrierwilson]

Summary

Additions needed to support the new "Amsterdam" theme. Changes are made in both the source and in the documentation.

Additions include:

• Registers and adds Amsterdam: Light and Amsterdam: Dark as options in the theme selector
• Creates new stylesheets for Amsterdam light and dark
• Make some minor changes to styling via the new stylesheets (so that theme selector can be tested)
  • Removes panel borders
  • Makes blue more saturated
• Adds information to CONTRIBUTING.md regarding how to help contribute to Amsterdam
• Adds checkmark to pull request template for checking changes against any new themes

Question

Should we even expose the new theme in the documentation? Or do we want to hide it behind a flag of some sort?

Checklist

• Checked in dark mode
  - [ ] Checked in mobile
• Checked in IE11 and Firefox
  - [ ] Props have proper autodocs
• Added documentation examples
  - [ ] Added or updated jest tests
• Checked for breaking changes and labeled appropriately
  - [ ] Checked for accessibility including keyboard-only and screenreader modes
• A changelog entry exists and is marked appropriately

[snide]

Should we even expose the new theme in the documentation? Or do we want to hide it behind a flag of some sort?

Yes. It's fine to expose.

Adds information to CONTRIBUTING.md regarding how to help contribute to Amsterdam

I did not see this. You might have missed a commit.

[snide]

I would suggest adding a new check mark onto https://github.com/elastic/eui/blob/master/.github/pull_request_template.md to reference that changes were checked against the new theme.

[johnbarrierwilson]

Ah! Yea, I'll add a check mark.

Weird! I had a strange push issue. I pushed, but it didn't like my upstream setup. Anyway, that should be included now. Just some minor tweaks to themeing.md

[cchaos]

The colors guideline page is not correctly pulling in the colors for the Amsterdam theme. You will want to look at this file to ensure the right colors file is being imported.

[snide]

The colors guideline page is not correctly pulling in the colors for the Amsterdam theme.

That file should give you what you need. You'll want to import the new theme at the top using the sass loader, and then trigger it here.

https://github.com/elastic/eui/blob/master/src-docs/src/views/guidelines/colors.js#L155-L156

A similar check should be done on this page here.

https://github.com/elastic/eui/blob/master/src-docs/src/views/guidelines/sass.js

[cchaos]

✅ The scss imports are working
✅ The theme switcher is working
✅ The css and json files get compiled during build
✖️ The colors and sass guideline pages aren't pulling in the amsterdam colors
Q: What is the wiki/theme-development.md file supposed to contain? It is currently an empty page.

[johnbarrierwilson]

Ah! 🤦🏻‍♂️ That file (theme-development.md) wasn't supposed to be committed.

[johnbarrierwilson]

@cchaos These items have been taken care of now. Thanks again for the help! Let me know if there's anything else.

[cchaos]

Thanks for making those changes! Still had one comment about the PR checklist but other than that, LGTM 👍