feat: adds a feature to provide a list of already added tags

[iamdipanshusingh]

Merging this PR will close #6 and will add a feature where the user can set an initial list of tags, which might have been added previously.

This is personally tested by me.
And apart from implementing this feature, I've also updated the README.md accordingly and have modified the code a little bit (have made the if statements shorter). Also, I didn't notice while committing that Android studio has formatted the code, LMK if you want that like before.
LMK, if any further change is required from my end. 🙂

[iamdipanshusingh]

@eyoeldefare please draft this PR for now... it has some bugs need to fix that

[iamdipanshusingh]

@eyoeldefare I've fixed the encountered issue, and have done some more changes:
now, you don't need to define onTag and onDelete if you're passing the tags, the tags will be maintained internally. So, onTag & onDelete are optional now.

Apart from this, your code was breaking if onDelete and onTag are not provided, I've managed that as well.
Lastly, have a look at the assertion I've added.

You can merge it, if you want to. LMK if you want to add something, I'll be happy to hear.

[eyoeldefare]

Hey thanks for the contribution, I will review this soon.

[ondbyte]

would be great if you push it to pub!

[ondbyte]

would be great if you push it to pub!

[eyoeldefare]

would be great if you push it to pub!

I am a bit busy right now due to exam season. I can't promise you to push it to pub but will review it during spring break.

[iamdipanshusingh]

@ondbyte till then, you can use my version... I've merged my changes to my forked repo's master branch

[eyoeldefare]

Hey thanks for the pr again. I was very busy until just today.
I think everything checks out here.
I will push this to master.