improve each plugin README.md and unify their format

[nerd0geek1]

Description

I improved each plugin's README.md content and unified its format.

What I did is

• move #h1 tag to at the top of README.md(android_alarm_manager_plus, android_intent_plus, share_plus)
• fix broken image link(connectivity_plus, network_info_plus, package_info_plus, sensors_plus, share_plus)
• insert/fix GitHub Actions badge(all plugin)

Checklist

Before you create this PR confirm that it meets all requirements listed below by checking the relevant checkboxes ([x]).
This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See [Contributor Guide]).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (flutter analyze) does not report any problems on my PR.
• I read and followed the [Flutter Style Guide].
• I am willing to follow-up on review comments in a timely manner.

Breaking Change

Does your PR require plugin users to manually update their apps to accommodate your change?

• Yes, this is a breaking change (please indicate a breaking change in CHANGELOG.md and increment major revision).
• No, this is not a breaking change.

[vbuberen]

Thanks for your contribution. Would like to admit that some of readme files were already updated in other PRs:
#666, #667, #670

I would suggest to revert your changes in readme for share_plus, package_info_plus and sensors_plus, since they are modified in those mentioned PRs anyway.

[nerd0geek1]

@vbuberen
Thank you for reviewing my PR.

As you pointed out in #673 (comment), I deleted some commits from my PR.

Please review my PR again when you can.

[vbuberen]

Looks good. to me. Thanks for your contribution @nerd0geek1

[vbuberen]

@mhadaily Can I ask you to help us merge this PR? Seems like I can't enable additional required checks, so can't merge this PR.

[mhadaily]

Thank you both

[vbuberen]

I see a point to improve in current Actions setup - will open a few PRs soon to not run full checks for docs changes.

[mhadaily]

that would be great @vbuberen