Add policy for deleting CPC repo content

Closes #1346.

Signed-off-by: Tobie Langel <tobie@unlockopen.com>

Author: tobie

governance/GOVERNANCE.md

@@ -166,6 +166,12 @@ The pull request may be fast-tracked if two CPC members approve the fast-trackin
 
 CPC members may request fast-tracking of pull requests they did not author. In that case only, the request itself is also one fast-track approval. Upvote the comment anyway to avoid any doubt.
 
+### Removing obsolete content
+
+The CPC aims to keep this repository up to date and void of obsolte information. The default is therefore to remove obsolete information. It is always possible to open a pull request to re-include deleted information. Please explain the rationale for doing so in that case, and please make sure such information is clearly labeled as obsolete.
+
+In order to make it easier to search for deleted information in the website, it is recommended to pay particular attention to commit messages when deleting content. In particular, note what content is being removed and why.
+
 [cpc repo]: https://github.com/openjs-foundation/cross-project-council
 [CPC charter section 5]: ../CPC-CHARTER.md#section-5-responsibilities-and-expectations-of-the-cpc
 [cpc charter decision making]: ../CPC-CHARTER.md#section-9-decision-making