docs: Add issue and discussion triage guide documentation

[mcanouil]

Introduce a guide for triaging issues and discussions to improve project management and collaboration.

It will be discoverable at https://quarto.org/docs/triaging/index.html (as for https://quarto.org/docs/triaging/index.html).

Edit: I fixed few spelling from UK to US.

[!NOTE] This PR should/could be followed by a PR in Quarto CLI repository to add the link in the issue and discussion templates:

• https://github.com/quarto-dev/quarto-cli/tree/main/.github/DISCUSSION_TEMPLATE
• https://github.com/quarto-dev/quarto-cli/tree/main/.github/ISSUE_TEMPLATE

[cderv]

/deploy-preview

[github-actions[bot]]

🚀 Deployed on https://deploy-preview-1527.quarto.org

[cderv]

/deploy-preview

[github-actions[bot]]

📝 Preview Deployment

🔍 Full site preview: https://deploy-preview-1527.quarto.org

🔄 Modified Documents

• docs/triaging/index.qmd

[github-actions[bot]]

Successfully created backport PR for prerelease:

• #1690