docs(upgrade): Adds missing details.

[edonehoo]

Closes #4459

[patternfly-build]

Preview: https://patternfly-org-pr-4479-site.surge.sh

[edonehoo]

made a variety of changes to try and cover all open requests/issues related to this. if I missed anything please lmk!

@tlabaj:

• for Bug - Upgrade guide missing Chart changes #4454: this section https://patternfly-org-pr-4479-site.surge.sh/get-started/upgrade#charts
• for Bug - Add documentation to upgrade guide for removed isActive prop in ExpandableSection #4442: this section https://patternfly-org-pr-4479-site.surge.sh/get-started/upgrade#components (left a comment on this issue -- what more should I be saying about this?)

@adamviktora:

• for Mention css-vars-updater codemod package in the upgrade guide #4446: this section https://patternfly-org-pr-4479-site.surge.sh/get-started/upgrade#run-css-vars-updater (let me know if you think we should expand more)

and then cc @nicolethoen in general, per the things you suggested from your upgrade experiences

[nicolethoen]

I think this is an excellent iterative improvement! 🥇

[adamviktora]

Great update overall!

Regarding the css-vars-updater (#4446) I think the section is perfectly fine as the details are explained under the Run tokens-update section above + there is always a link to README.

I am not sure whether some of the Notable changes require that much manual attention (but I may be wrong, cc @nicolethoen) so I left some comments.

Also the Update React tokens section should be updated - left a comment there.

[adamviktora]

Looking great 🎉

[tlabaj]

Looks good. Just on little update neeeded