Adding information about indexers in C#

[Nilkamal]

NOTE:

• Please fill out the template below

Did you read the instructions in the README?

Y

Have you read the instructions in CONTRIBUTING?

Y

Have you written this article by yourself? Have you taken inspiration from anywhere and then written it in your words?

I have written this article by myself. It is written based on my practical experience with C# language.

[the-ethan-hunt]

Please read the readme.md before pulling a PR

[RN0311]

@Nilkamal : We appreciate your contribution, can you please have a look at README.md before submitting a PR!

[Nilkamal]

@RN0311 can you please give some direction?

[RN0311]

@Nilkamal : Our main motive is to have "simple introductory guides" which doesn't necessarily involves "coding". Please have a look at an excellent PR- #66
I hope, this helps!

[the-ethan-hunt]

Closing this PR due to stagnation.