Fixed #105 - Section interface should have a label field

[anujchoudhary-17]

Sorry for the chaos in the last PR. Added label string as an optional variable field in the Section interface. In the op-js/src/index.ts file I have made the following changes. Please review it and let me know if any further changes are required :)

@jodyheavener Are there any other issues you feel like I can work one? Please let me know. Would love to work on new issues

Thank you

[jodyheavener]

Hi @anujchoudhary-17 this looks great, thank you for fixing this!

In terms of other issues, it would be best to review issues in our various open source repos and contribute where you feel like you might do best. Some repos include:

• op-js (this one)
• op-vscode
• docusaurus-extensions
• shell-plugins
• typeshare