In the extension, currently we do the following:
1. check whether there's at least one React renderer on the page
2. if yes, load the backend to the page
3. initialize the backend
To support multiple versions of backends, we are changing it to:
1. check the versions of React renders on the page
2. load corresponding React DevTools backends that are shipped with the
extension; if they are not contained (usually prod builds of
prereleases), show a UI to allow users to load them from UI
3. initialize each of the backends
To enable this workflow, a backend will ignore React renderers that does
not match its version
This PR adds a new file "backendManager" in the extension for this
purpose.
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I've tested it on Chrome, Edge and Firefox extensions
Mengdi Chen