fix: Svelte tutorial warning removals and corrections

[michael-255]

The Svelte team has done a great job with both the tutorials and the entire docs site!

I took note of a few things to fix while working through them. There isn't a specific issue for any of these changes that I could find.

Before submitting the PR, please make sure you do the following

• It's really useful if your PR references an issue where it is discussed ahead of time.
• Prefix your PR title with feat:, fix:, chore:, or docs:.
• This message body should clearly illustrate what problems it solves.

Changes

Added minimum needed attributes to remove the aria warnings on AudioPlayer.svelte in several tutorials.

Advanced Bindings, Dimensions:
Allow input box to be clickable if user deletes all text. This one caught me briefly.

Svelte Element:
Added a TODO comment to make it clear where the user should put the svelte:element block.
Using &amp in the instruction example so the user doesn't attempt to use <{selected}> directly which will cause this error:

Error compiling App.svelte

Expected a valid element or component name. Components must have a valid variable name or dot notation expression
https://svelte.dev/e/tag_invalid_name

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