Updated esversion to 11 from 7 to fix warnings related to nullish assingment

[Chaitanya1672]

Fixes #3146

Changes:
I have updated esversion from 7 to 11 to resolve warnings related to nullish assignment.
I have Updated Editor/index.js to set the CodeMirror instance with the updated esversion.

Before:-

After:-

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[raclim]

Thanks so much for catching and fixing this, this is great!