Null safety support

[babulpatel1309]

• Added null safety and updated dependencies.

[pinkfish]

I did an update to null safety. Is this still needed?

[babulpatel1309]

@pinkfish if everything is working as expected then we're good to go :)
The PR was actually generated on 19th May 🤣 . At that moment so many libraries were missing this part, so i sat and raised PR for all libraries.

[babulpatel1309]

@pinkfish i coudn't able to find where exactly did you publish the null safety update?

[philipgiuliani]

@pinkfish you have updated to null safety in the master branch but not in the main branch.

[fotiDim]

@philipgiuliani why is there both a master and a main branch? For sound null safety sdk: ">=2.12.0 <3.0.0" should be defined in pubspec.yaml. I see that this is the case only in master and not main.