docs: add loadPartialConfig info in README

[gaurav5430]

To make it more clear that the options specified here override the existing babel config/

Please Read the CONTRIBUTING Guidelines
In particular the portion on Commit Message Formatting

Please check if the PR fulfills these requirements

• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:
  changes to README

What is the current behavior? (You can also link to an open issue here)
N/A

What is the new behavior?
remains the same

Does this PR introduce a breaking change?

• Yes
• No

If this PR contains a breaking change, please describe the following...

• Impact:
• Migration path for existing applications:
• Github Issue(s) this is regarding:

Other information:
related to #823

[kylemh]

I appreciate the added documentation, but writing "Kind of fixes #823" ensures this PR's merge will close that ticket. I don't believe this resolves the root problem I'm outlining in the issue.

[gaurav5430]

I appreciate the added documentation, but writing "Kind of fixes #823" ensures this PR's merge will close that ticket. I don't believe this resolves the root problem I'm outlining in the issue.

Sure, removed that.
Thanks.

[JLHwung]

Closing this PR. This will be addressed in #909