Added constructors for DiracDelta with Triangulation argument.

[shagun751]

DiracDelta definitions were limited to DiscreteModel{D} argument. Introduced constructors for DiracDelta with Triangulation{Dt} argument.
Added the tests for the same in DiracDeltaTests.jl as well.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.35%. Comparing base (6db1059) to head (512129b).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1087   +/-   ##
=======================================
  Coverage   89.35%   89.35%           
=======================================
  Files         197      197           
  Lines       23916    23935   +19     
=======================================
+ Hits        21370    21388   +18     
- Misses       2546     2547    +1     

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[JordiManyer]

Hi @shagun751 , thank you for your contribution! Could you add a new entry to NEWS.md? I will merge your PR after that.
Thank you!

[shagun751]

@JordiManyer I have updated NEWS.md as per convention.
Thank you!