chore: migrate Renku doc links from Notion to docs.renkulab.io

[andre-code]

PR to migrate Renku doc links from Notion to docs.renkulab.io.

✅ Updated / Added Links

• Migration guide
  From: https://renku.notion.site/How-to-migrate-a-Renku-1-0-project-to-Renku-2-0-1ac0df2efafc80a88e58e2b3db035110
  To: https://docs.renkulab.io/en/latest/docs/users/migrate-v1-v2/migrate-renku-1-project-to-renku-2

• Using a custom Docker image
  From: https://renku.notion.site/How-to-use-your-own-docker-image-for-a-session-launcher-11f0df2efafc80af848ffcaf9ccff31c
  To: https://docs.renkulab.io/en/latest/docs/users/sessions/guides/use-your-own-docker-image-for-renku-session

• Community / Get help
  From: https://renku.notion.site/Renku-Community-Portal-2a154d7d30b24ab8a5968c60c2592d87
  https://renku.notion.site/Get-help-1a2b4b7b0e4746769e246c0328d3d3ad
  To: https://docs.renkulab.io/en/latest/docs/users/community

• Documentation home
  From: https://renku.notion.site/Documentation-db396cfc9a664cd2b161e4c6068a5ec9
  To: https://docs.renkulab.io/en/latest/

• Research
  From: https://renku.notion.site/Renku-for-Data-Scientists-21d46b16e76e4bc484add8367c44f884
  To: https://docs.renkulab.io/en/latest/docs/users

• Teaching
  From: https://renku.notion.site/Renku-for-Teaching-1460df2efafc809cb134d2a4e32ed90e
  To: https://docs.renkulab.io/en/latest/docs/users/use-cases/teaching/set-up-course-in-classic-mode

• Quick start / Getting started
  From: https://renku.notion.site/Get-started-with-Renku-1a50df2efafc800f8554e30fd7458fa6
  To: https://docs.renkulab.io/en/latest/docs/users/getting-started

• Migrate away from GitLab
  From: https://renku.notion.site/How-to-migrate-out-of-RenkuLab-GitLab-2700df2efafc80c2b442c3ad981d86fc
  To: https://docs.renkulab.io/en/latest/docs/users/migrate-v1-v2/migrate-from-gitlab

• Create a project
  From: https://www.notion.so/renku/How-to-create-a-new-project-eea72bea221848d7bd0b3338dd859504
  To: https://docs.renkulab.io/en/latest/docs/users/getting-started/create-project

• Create environment with custom packages
  From: https://renku.notion.site/How-to-create-a-custom-environment-from-a-code-repository-1960df2efafc801b88f6da59a0aa8234
  To: https://docs.renkulab.io/en/latest/docs/users/sessions/guides/create-environment-with-custom-packages-installed

• How Renku works / About
  From: https://renku.notion.site/Why-Renku-1900df2efafc80839b26cbad43f24778
  To: https://docs.renkulab.io/en/latest/docs/users/knowledge-base/about

Note:
pending create a updated version of https://docs.renkulab.io/en/0.70.0/how-to-guides/admin/incidents-maintenance.html
and https://renku.notion.site/Renku-for-Events-18c0df2efafc800bb26ae93333b4318d

fix #3948
/deploy renku=release-2.13.0

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ui-3958.dev.renku.ch

[leafty]

LGTM, thanks 👏

[RenkuBot]

Tearing down the temporary RenkuLab deplyoment for this PR.