Add Dependabot workflow for flutter dependency Updates

[prajapatihet]

Is your feature request related to a problem? Please describe.
As your project has so many dependencies and it will frustating while updating one by one

Describe the solution you'd like
So Add DependaBot to .github folder So it will automatically update that dependency at some periodic time

Assign to me @Pratikdate
I am GSSoc Contributor

[Shubham-Zone]

@Pratikdate please assign this to me i am GSSOC'24 contributor and have 2+ years of experience in flutter

[heysagnik]

hey @prajapatihet you are good to go

[prajapatihet]

@heysagnik Could you please assign the appropriate labels?

[prajapatihet]

Please review PR and assign appropiate lebels!!