docs: Add Web UI documentation on repo structure

[adchia]

What this PR does / why we need it:
This adds a lot more documentation on the Feast Web UI documentation and the release process. Also updates the feast ui bundled UI to always use the latest npm package

Which issue(s) this PR fixes:

Fixes #

[adchia]

cc @AlexEijssen

[codecov-commenter]

Codecov Report

Merging #3014 (f4961bf) into master (d4af068) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3014      +/-   ##
==========================================
- Coverage   78.03%   78.01%   -0.02%     
==========================================
  Files         193      193              
  Lines       16446    16445       -1     
==========================================
- Hits        12833    12830       -3     
- Misses       3613     3615       +2     

Flag	Coverage Δ
integrationtests	66.90% <ø> (-0.86%)	⬇️
unittests	60.05% <ø> (+0.16%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
sdk/python/feast/infra/online_stores/datastore.py	87.96% <0.00%> (-1.39%)	⬇️
...ests/integration/registration/test_sql_registry.py
sdk/python/tests/unit/test_sql_registry.py	94.05% <0.00%> (ø)
...east/infra/materialization/lambda/lambda_engine.py	93.75% <0.00%> (+1.04%)	⬆️

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[felixwang9817]

/lgtm

[feast-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: adchia, felixwang9817

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