Update transition:persist known limitations for canvas preservation

[SvetimFM]

Companion to withastro/astro#15728 (merged).

The transition:persist known limitations note currently says:

Not all state can be preserved in this way. The restart of CSS animations and the reload of iframes cannot be avoided during view transitions even when using transition:persist.

With the merged fix, canvas elements (including WebGL/WebGL2 context and drawn content) are now preserved during persist swaps. The note should be updated to clarify this — something like appending:

Canvas elements, including WebGL/WebGL2 context and drawn content, are preserved.

PR was at #13339 but docs are in v5 freeze. Happy to re-submit after v6 launches.

[martrapp]

Besides fixing WebGL context loss, @SvetimFM's PR also switched handling of persisted elements to the modern moveBefore function, which is now supported by all modern browsers, but Safari. In supporting browsers, reset of CSS transitions and reloading iframes should not happen anymore.

I would therefore suggest softening this to:

Most modern browsers preserve internal DOM state across view transitions, but in Safari and older versions of other browsers, issues such as CSS animations restarting or iframes reloading may still occur when using transition:persist.

All suggestions for improvement are, as always, very welcome!