Add: Window.saveTextAs(string)

[AleziaKurdis]

It would open a lot of opportunity to implement the following method:

Window.saveTextAs(string)

When called, it would open a save dialog to determine the name and the path of where to save a file containing the string pass in parameter as content.

With this I could implement js side a sav to serverless functionality, bit it would open to a lot of other usage too.

Using a dialog would also keep this relatively safe by ensuring that the user do it intentionally.

[JulianGro]

Maybe we should have another optional parameter for the file name and one for file external? In the example of a serverless, the file extension would need to be .json, so having that potentially prefilled would be great.