DOC: update docs to use github pages

[codecov-commenter]

Codecov Report

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

Project coverage is 95.12%. Comparing base (59ad282) to head (857e4c6).

:exclamation: Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #87 +/- ## ======================================= Coverage 95.12% 95.12% ======================================= Files 11 11 Lines 799 799 ======================================= Hits 760 760 Misses 39 39 ``` | [Flag](https://app.codecov.io/gh/ColmTalbot/gwpopulation/pull/87/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Colm+Talbot) | Coverage Δ | | |---|---|---| | [python3.10](https://app.codecov.io/gh/ColmTalbot/gwpopulation/pull/87/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Colm+Talbot) | `94.99% <ø> (ø)` | | | [python3.11](https://app.codecov.io/gh/ColmTalbot/gwpopulation/pull/87/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Colm+Talbot) | `94.99% <ø> (ø)` | | | [python3.9](https://app.codecov.io/gh/ColmTalbot/gwpopulation/pull/87/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Colm+Talbot) | `94.99% <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=Colm+Talbot#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.