Allow setting spanned spanned content with processing

[khaykov]

Fix

In this PR we add a method for setting a spanned content, that will process it before setting it into the editor. This is useful if you want to parse HTML into Spanned text somewhere else (eg, on a different thread which is useful if you only use Aztec to display content).

Test

1. Make sure demo app work, and content is being set.

• If there are new strings that have to be translated, I have added them to the client's strings.xml as a part of the integration PR.

[zwarm]

@khaykov - this is a nice improvement. The demo app is working as expected. 👍