docs: Updated Readme.md for companies using Argo:

[praneetchandra]

Added Peak.ai in the companies list that officially using Argo. We at Peak are developing a new product feature that is machine learning code workflow as a service based on Argo workflows/DAG.

Checklist:

• Either (a) I've created an enhancement proposal and discussed it with the community, (b) this is a bug fix, or (c) this does not need to be in the release notes.
• The title of the PR is (a) conventional, (b) states what changed, and (c) suffixes the related issues number. E.g. "fix(controller): Updates such and such. Fixes #1234". Why? for the release notes.
• Optional. I've added My organization is added to the README.
• I've signed the CLA and required builds are green.

[claassistantio]

All committers have signed the CLA.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@7e9b2b5). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #1916   +/-   ##
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  Coverage          ?   10.65%           
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  Files             ?       35           
  Lines             ?    24931           
  Branches          ?        0           
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  Hits              ?     2657           
  Misses            ?    21935           
  Partials          ?      339

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[alexec]

LGTM.Welcome!