fix(#99): replace xml formatting, prevent double format

[followynne]

This PR fixes #99. It

• pretty-prints XML only on first modal opening
• replaces custom XML formatting with external library

[mo-esmp]

@followynne After reviewing and merging PRs 95 and 98, would you like to publish the nuget package yourself?

[followynne]

@mo-esmp

That's fine, as you like 😊
If you want, I could try fixing the datetime rendering issue and publish a nuget beta with the latest changes, to let users test it and do a first nuget publish?

[mo-esmp]

It sounds good to me. Let's publish a beta version first and thanks again for your effort.

[followynne]

Awesome! Thanks a lot to you 🤗