Add DML Insert and Update examples to README

[jsimonweb]

No description provided.

[jdpedrie]

Can we make the general conventions on the new samples line up with the existing examples? i.e., don't wrap in a function and use SpannerClient::connect() with dummy string values.

[dwsupplee]

Thanks @jsimonweb! :)

I agree with @jdpedrie on keeping the samples in line with what we already have.

Also, If we add these alongside some of our existing snippets we'd be able to take advantage of our snippet testing suite to make sure the samples don't fall out of date in the future. Traditionally we've tried to keep the samples in the READMEs pretty dry for this very reason.

[codecov]

Codecov Report

Merging #2121 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2121   +/-   ##
=========================================
  Coverage     92.57%   92.57%           
  Complexity     4379     4379           
=========================================
  Files           304      304           
  Lines         13014    13014           
=========================================
  Hits          12048    12048           
  Misses          966      966

---

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 df8d42b...7815d62. Read the comment docs.

[codecov]

Codecov Report

Merging #2121 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2121   +/-   ##
=========================================
  Coverage     92.57%   92.57%           
  Complexity     4379     4379           
=========================================
  Files           304      304           
  Lines         13014    13014           
=========================================
  Hits          12048    12048           
  Misses          966      966

---

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 df8d42b...7815d62. Read the comment docs.

[dwsupplee]

Closing in favor of #2269