Bevy tracking link in README badge is broken

[manankarnik]

Description

Bevy has moved its plugin guidelines to the Bevy Book on the website. As a result, the bevy tracking link is broken. Willing to create a PR for the same if required.
See bevyengine/bevy#11272

Possible Fixes

• Update the tracking link in badge to https://bevyengine.org/learn/book/plugin-development/#main-branch-tracking
• Provide a section in README explaining the badge and link to it
• Remove the badge from README
• Do nothing

[giusdp]

Oh thank you for the heads up! I think it's fine to just update the tracking link. If you want go ahead :)