Videos: Add .m2ts to known file extensions

[koztya]

MTS is supported file format, but supported extension is only .mts.
.m2ts is valid file extension of the format. Please add this file extension to the list.
https://en.wikipedia.org/wiki/.m2ts

[lastzero]

We will provide an updated development preview shortly so you can test these changes. Thank you very much!

[lastzero]

An updated preview build will be available for testing soon:

• https://docs.photoprism.app/release-notes/#development-preview

We hope you have a few minutes to let us know if it works so we can release this in our next update!

[lastzero]

@koztya Happy testing! 🎁

[koztya]

I've tested preview - it found my .m2ts files normally.

@lastzero thanks, very fast, wow! :-)

[lastzero]

Thanks for testing! 👍