Add momentum calculator

[Amit366]

Is your feature request related to a problem? Please describe.
Add momentum calculator

Describe the solution you'd like

In classical mechanics section add the topic momentum and then in that add the formula along with some contents.
(On clicking classical mechanics it should open a contents page where there would be different topic names. Then on clicking the topic name a page should open where there is some content with images and then below it the calculator.)

[github-actions]

Hi 😄, @Amit366 Thanks for creating an issue at FunwithPhysics. We request you to follow the contributing guidelines.

[souravseal99]

Hi @Amit366 , I would like to work on it, can we discuss a bit more about this issue..

[Amit366]

@souravseal99 heyy u can dm me on slack. If u have any doubt.