add swap sim example

[Evan-Kim2028]

• extracted test_swap_sim test into an example file
• write docs for sync and pool

[Evan-Kim2028]

Not sure why the test suite is failing, I didn't touch any code that should affect those tests.

Regarding rustfmt fail, I adjusted the doc lines to conform to rustfmt line size

[Evan-Kim2028]

Ran cargo fmt and cargo clippy --fix

[0xKitsune]

Thanks for making this PR! I think we should probably separate the docs into a separate PR. I think that there are a few places where some additional information and rewording could be useful, but we can get the examples merged in once the changes requested are made.