feat: add templating mode selector

[paoloricciuti]

This allow us to play around and see the output of with sveltejs/svelte#15538 and sveltejs/svelte#15599 ...when we merge something like this we can change this PR to only show the selector in those specific versions.

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Name	Status	Preview	Updated (UTC)
svelte-dev	✅ Ready (Inspect)	Visit Preview	May 23, 2025 1:16pm

[Rich-Harris]

The html option should be checked by default:

Might also be good to bump up the default height of the compiler options pane to accommodate the extra row

[paoloricciuti]

Fixed both

[Ocean-OS]

Found a bug where moving from one example to the other removes the option entirely, found by moving from the "hello world" example to the "reactive assignments" example

[paoloricciuti]

Found a bug where moving from one example to the other removes the option entirely, found by moving from the "hello world" example to the "reactive assignments" example

Thanks...I also showed it with latest and that fixed the issue...if we can merge this today so i can show it on TWIS it would be great (otherwise I'll use the preview version)