Add docstrings for new stream class, update sphinx docs

[amitschang]

Adding some docstrings for new classes and methods. Also subbing out some pages for the manual.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (05b00bb) 100.00% compared to head (53f2768) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #44 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 11 11 Lines 551 551 ========================================= Hits 551 551 ``` | [Flag](https://app.codecov.io/gh/ssec-jhu/dplutils/pull/44/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssec-jhu) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/ssec-jhu/dplutils/pull/44/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssec-jhu) | `100.00% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=ssec-jhu#carryforward-flags-in-the-pull-request-comment) to find out more.

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[amitschang]

@jamienoss , thanks, I probably should have run a spell-checker - and I had no idea I had such a tendency to type yeilded 😆

[amitschang]

Thanks. And to be clear, it doesn't overcommit in the sense that more tasks than resources run expecting that some will not use what they request. Ray will ensure that the resources requested are guaranteed for the task (e.g. if you have 8 cores and tasks using 5 and 4, both will not run at the same time)

[jamienoss]

Ok, good to know - I guess I misunderstood a comment in #43 but never mind. Maybe I'm just misremembering it lol.