Add description to secrets

[laurentS]

Clear and concise description of the problem

A repo can use many secrets, some of which may have non-obvious origins. I find it would be useful to be able to add notes to a secret, which could contain any information that the user deems helpful for them. An example use case would be:
secret_name: SOME_API_TOKEN
secret_value: <super_secret_value>
description: "Used by process xxx. Expiry date: ddmmyy, renew by going to ..., include API scope blablabla"

Suggested solution

This could be a simple plain text field, visible to anyone who has access to create/modify secrets, along with the secret name. The aim is to provide hints/document the secret.
I noticed that gitlab recently added this to their CI, which I find extremely helpful.
In a perfect world, secrets would be generated in code, with proper documentation, but it's not always possible in tiny projects.

Alternative

No response

Additional context

No response

Validations

• Checked that the feature isn't part of the next version already [https://woodpecker-ci.org/faq#which-version-of-woodpecker-should-i-use]
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.