[camera] Update README

[stuartmorgan-g]

• Removes some obsolete references to the current state
• Adds an OS support chart
• Minor cleanup

Fixes flutter/flutter#83722
Part of flutter/flutter#84200 and flutter/flutter#34999

Pre-launch Checklist

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• I read the Tree Hygiene wiki page, which explains my responsibilities.
• I read and followed the relevant style guides and ran the auto-formatter. (Unlike the flutter/flutter repo, the flutter/plugins repo does use dart format.)
• I signed the CLA.
• The title of the PR starts with the name of the plugin surrounded by square brackets, e.g. [shared_preferences]
• I listed at least one issue that this PR fixes in the description above.
• I updated pubspec.yaml with an appropriate new version according to the pub versioning philosophy, or this PR is exempt from version changes.
• I updated CHANGELOG.md to add a description of the change, following repository CHANGELOG style.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.

[stuartmorgan-g]

@blasten @ditman @jmagman What do you think of the OS support chart here? This is a proposal for what to roll out across all of our plugins as part of flutter/flutter#34999 and flutter/flutter#84200 so if we want a different format we should decide now if possible.

(An alternative I considered was to make it a vertical table so there's more room for inline notes, but having the table compact and linking out for notes seemed like the better option.)

[jmagman]

Here's what the table looks like:

(An alternative I considered was to make it a vertical table so there's more room for inline notes, but having the table compact and linking out for notes seemed like the better option.)

I think the compact table and asterisk for notes that you have now makes sense. LGTM

[stuartmorgan-g]

@blasten @ditman Thoughts on this table format for Android and Web dependencies?

[ditman]

I like this, thanks for doing it!

In general all the _web plugins (should) have a README with what's supported/not supported by the web with regards to the plugin (or by each browser in particular), so linking to those docs is a good idea.

(I wish we could open the link in a new tab, but users can always center-click to not lose track of what they were reading so far.)

Also: are we going to have all supported platforms as columns? That might be a lot of columns? :)

[stuartmorgan-g]

Also: are we going to have all supported platforms as columns? That might be a lot of columns? :)

That's why I'm trying to keep them very short. I considered it as rows, but having potentially 6 rows seemed much more disruptive to the flow of the README.