enable preview for SVG

[couzteau]

fix #5124 - Enables to load SVG files into live preview. However the preview is not live as for HTML, meaning changes to the SVG need to be saved before they are visible in the browser preview. This limitation is currently due to the use of XML namespaces in SVG tags. Brackets currently has no way to honor XML namespaces in markup.

[njx]

I'll need to double-check this--as I commented in another similar issue (#5058), adding the extension to this list might make us try to do live-as-you-type updating. I'll take a look and see if this is good enough or if we have to do something else.

[njx]

Unfortunately, as I suspected, it's not quite this simple, because we need a way to disable live editing in these files.

It's not totally clear the right way to do this. It seems like there are two choices: (1) don't create an HTMLDocument for these kinds of files, or (2) create an HTMLDocument but have StaticServer not call setInstrumentationEnabled on it. (2) seems safer, mostly because I don't actually know what the ramifications of (1) are (it might just not work, since Live Development might assume we always have a "live document" for the main previewed file).

Given that this is no longer trivial, and the original request was opportunistic anyway, I think we should move this bug out of the sprint, and possibly tag it move to backlog. @couzteau what do you think?

[njx]

Closing since we would need to do more work to make this work and it's not a priority for this sprint.