DOC-648 Add pages for Neptune and W&B plugins

[neverett]

Why are the changes needed?

Adds docs pages for Neptune and W&B plugins.

This is one of three PRs we need to merge in the following order to get the neptune and wandb flytekit plugin docs onto the docs site:

1. flytesnacks PR to fix refs in neptune and wandb plugin docs
2. flyte PR to update monodocs dependencies
3. flytekit PR (this one) to add new flytekit plugin docs for neptune and wandb plugins (after re-running monodocs build)

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

[neverett]

Seeing the following monodocs build error:

 sphinx.errors.SphinxWarning: Failed to import flytekitplugins.neptune.
Possible hints:
* AttributeError: module 'flytekitplugins' has no attribute 'neptune'
* ModuleNotFoundError: No module named 'neptune'

/cc @thomasjpfan @cosmicBboy

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.45%. Comparing base (cd8216a) to head (3c1ea46).
Report is 12 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #2803       +/-   ##
===========================================
+ Coverage   76.82%   94.45%   +17.63%     
===========================================
  Files         196       24      -172     
  Lines       20301      794    -19507     
  Branches     2610        0     -2610     
===========================================
- Hits        15596      750    -14846     
+ Misses       4004       44     -3960     
+ Partials      701        0      -701     

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[cosmicBboy]

Do we need to update docs requirements to fix docs build error?

[neverett]

Do we need to update docs requirements to fix docs build error?

Yeah, we can try that -- the current docs requirements file doesn't list every plugin, only flytekitplugins-deck-standard, flytekitplugins-kfpytorch, and flytekitplugins-sqlalchemy, although it does list a lot of plugin dependencies.

[neverett]

After testing locally, it looks like we need to add wandb and neptune to the monodocs requirements -- will open a flyte PR shortly.