livereload: Close connection on pageshow

[bep]

Note that this PR doesn't fully fix the issue, as in

• LiveReload.connector.disconnect() on pagehide fixes the problem.
• But I have not found a way to "restart" the websocket connection, which means that the LiveReload stops working.
• Note that if you make any changes to the JS, run go generate ./livereload/gen.

Fixes #13287

[github-actions]

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