feat: add .repo-metadata.json, start generating README.md

[bcoe]

This adds a .repo-metadata.json, which is used to automate publishing docs when new package versions are released.

This PR also re-runs our automated README generation, which is based on .repo-metadata.json as well.

I've left a couple questions for folks inline.

[bcoe]

Is renaming this region tag to the standard quickstart okay? CC: @sduskis, @JustinBeckwith, I wasn't sure how load bearing the region tag is, e.g., will this mean that we break samples on cloud.google.com?

[JustinBeckwith]

That is very likely to break samples. Can you follow up with @jmdobry or @fhinkel on the right way to change this?

[codecov]

Codecov Report

Merging #636 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #636   +/-   ##
=======================================
  Coverage   97.89%   97.89%           
=======================================
  Files          14       14           
  Lines         856      856           
  Branches      178      178           
=======================================
  Hits          838      838           
  Misses          2        2           
  Partials       16       16

---

Continue to review full report at Codecov.

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[codecov]

Codecov Report

Merging #636 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #636   +/-   ##
=======================================
  Coverage   97.89%   97.89%           
=======================================
  Files          14       14           
  Lines         856      856           
  Branches      178      178           
=======================================
  Hits          838      838           
  Misses          2        2           
  Partials       16       16

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 884711f...47e3928. Read the comment docs.

[JustinBeckwith]

LGTM, with the nit about the region tag

[JustinBeckwith]

That is very likely to break samples. Can you follow up with @jmdobry or @fhinkel on the right way to change this?