Made changes to CONTRIBUTING.md file

[Jassi10000-zz]

Issue Number

fixes #191

Describe the changes you've made

In CONTRIBUTING.md file , in the section of using Yarn as a package manager :

1 .I added the guideline to install the package using Yarn which was was not present previously in the documentation

2. I changes the heading " Running in Deployment Mode " to " Running in Development Mode " for Yarn Section Heading

Describe if there is any unusual behavior (Any Warning) of your code(Write NA if there isn't) NA , there was only a lil correction in the documentation

Additional context (OPTIONAL)

Test plan (OPTIONAL)

A good test plan should give instructions that someone else can easily follow.

Checklist

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] All new and existing tests passed.
• [x] The title of my pull request is a short description of the requested changes.

[Jassi10000-zz]

@rajatgupta24 Made the changes successfully Thanks for the opportunity