Fix the Lite custom element to initialize the app in the connected callback and dispose the app in the disconnected callback

[whitphx]

Description

The custom element <gradio-lite /> is not working for example when it's dynamically created by Svelte.
Ref: https://stackoverflow.com/q/63066330/13103190 (actually, Svelte uses createElement internally to create DOMs)

[gradio-pr-bot]

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Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/e4e790e1bec53842a192bfadfa1cc863c36f9e93/gradio-4.20.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@e4e790e1bec53842a192bfadfa1cc863c36f9e93#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/app	minor
gradio	minor

• Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Fix the Lite custom element to initialize the app in the connected callback and dispose the app in the disconnected callback

Maintainers or the PR author can modify the PR title to modify this entry.

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• If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can update the changelog file directly.

[pngwn]

Looks great. Thanks @whitphx!

[abidlabs]

Likewise I'll get this in for the release! cc @aliabd