docs: update rendering instructions

[maelle]

My mistake!

Closes #60.

[krlmlr]

Currently likely blocked by #57?

[github-actions[bot]]

Summary

Status	Count
🔍 Total	927
✅ Successful	885
⏳ Timeouts	0
🔀 Redirected	0
👻 Excluded	40
❓ Unknown	0
🚫 Errors	2

Errors per input

Errors in docs/posts/2020-12-23-dynamic-gha/index.html

• [429] https://www.gnu.org/software/sed/manual/sed.html | Failed: Network error: Too Many Requests

Errors in docs/posts/2024-09-09-zurich-roadcycling-wc-2024/index.html

• [403] https://support.strava.com/hc/en-us/articles/216919447-Elevation | Failed: Network error: Forbidden Full Github Actions output

[maelle]

I commented there, thank you!