fix: Grammatical error & typo in CONTRIBUTING.md

[debajoti]

All Submissions:

• Have you followed the guidelines stated in CONTRIBUTING.md file?
• Have you checked to ensure there aren't any other open Pull Requests for the desired changed?

Type of change

• This change requires a documentation update

New Feature Submission:

• Does your submission pass the tests?
• Have you linted your code locally prior to submission?

Changes To Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

After these steps, you're ready to open a pull request.

a. Give a descriptive title to your PR.

b. Describe your changes.

c. Put `closes #XXXX` in your comment to auto-close the issue that your PR fixes (if such).

[debajoti]

@masenf