Link to contribution guide in bot messages for priority/low and priority/normal

### Description

When bug is triaged with `action/priority/low` or `action/priority/normal` , the bot will display the message about issue not being priority and about the fact that we will welcome contribution. In particular there is this sentence in the end:
```
We would also welcome a contribution to fix the issue.
```

Was wondering if it is useful to add link to the contributions guide somehow - https://github.com/keycloak/keycloak/blob/main/CONTRIBUTING.md ? It can possibly slightly increase probability that contribution will be sent and it will be of good quality. If the text is too long, can we add just the link to the guide without additional text? Something like:
```
We would also welcome a contribution to fix the issue.
```

### Discussion

_No response_

### Motivation

_No response_

### Details

_No response_

Locate the bot-message templates or entry points handling action/priority/low and action/priority/normal. Read the existing priority-notification tests, if present, and verify the generated messages contain a link to CONTRIBUTING.md without breaking their formatting.

Written by the indexing model from the issue text.