feat(api-reference): add typedoc plugins for api reference

[AllanZhengYP]

Description of changes:
This change adds 2 typedoc plugins:

1. client-documentation-generator: It is used when generating each client level api reference
   

2. Private core-packages-documentation-generator: It generates the landing page for the SDK. It landing page includes links to docs of all the dependency packages in packages, and links to all the docs for each client:
   
   

So the overall API reference is generated in 2 batches:

1. Build each client's doc by yarn build-documentation --out docs. It will generate docs for each client under docs folder
2. Build packages docs and link the clients module to the landing page. In the project root: yarn build-documentation --clientDocs clients/{{CLIENT}}/docs

In each step, users can specify the output path with out argument.

TODO:

1. Regenerate clients with correct Typedoc options

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-io]

Codecov Report

Merging #1694 (690fea5) into master (de75f7e) will decrease coverage by 0.07%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1694      +/-   ##
==========================================
- Coverage   79.77%   79.70%   -0.08%     
==========================================
  Files         325      328       +3     
  Lines       12087    12571     +484     
  Branches     2553     2670     +117     
==========================================
+ Hits         9643    10020     +377     
- Misses       2444     2551     +107     

Impacted Files	Coverage Δ
...tocol_tests/aws-restxml/commands/XmlMapsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlBlobsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlEnumsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ocol_tests/aws-restxml/commands/XmlListsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...col_tests/aws-restjson/commands/JsonMapsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonBlobsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonEnumsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...ol_tests/aws-restjson/commands/JsonListsCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...tests/aws-restxml/commands/XmlAttributesCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
...tests/aws-restxml/commands/XmlNamespacesCommand.ts	95.65% <0.00%> (-4.35%)	⬇️
... and 104 more

---

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 9a62c0a...690fea5. Read the comment docs.

[trivikr]

nit: update title to feat(docs)?

[github-actions]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs and link to relevant comments in this thread.