Add contribution guidelines

[gauthamzz]

• comment before solving issues.
• solve merge conflicts.
• follow proper code indentation.
  And other standard norms

[ananya]

would like to solve this.

[adityaraj-xtc]

i would like to work on this

[gauthamzz]

assigned to @ananya-agrawal , since she commented first.
also @brain-sick do only one issue at a time for now