Adds guidance about error boundaries to React.lazy docs

[jeffposnick]

Fixes #915

Changes proposed in this pull request:

• Adds a new section that describes using an error boundary to handle lazy-loading failures.

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[housseindjirdeh]

Soo good, thank you so much for adding this :)

Literally two of the tiniest nits but otherwise this looks great. Also please add yourself as an author!

authors:
  - houssein
  - jeffposnick

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[jeffposnick]

Feedback addressed!

I think @robdodson still needs to approve/merge?

[housseindjirdeh]

Yep, needs a codeowner approval

@robdodson I know we were experimenting with having multiple codeowners before. Will it be easier if I was also a codeowner for the react/ directory?

[robdodson]

@robdodson I know we were experimenting with having multiple codeowners before. Will it be easier if I was also a codeowner for the react/ directory?

Sure thing, I'll put together a PR to add you.