Remove references to discourse.joinmastodon.org (mastodon#17797)

Remove broken CODEOWNERS file

Add sponsor.joinmastodon.org to FUNDING.yml

.github/FUNDING.yml

@@ -1,3 +1,3 @@
 patreon: mastodon
 open_collective: mastodon
-github: [Gargron]
+custom: https://sponsor.joinmastodon.org

.github/ISSUE_TEMPLATE/2.feature_request.yml

@@ -1,5 +1,6 @@
 name: Feature Request
 description: I have a suggestion
+labels: suggestion
 body:
   - type: markdown
     attributes:

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,8 @@
 blank_issues_enabled: false
 contact_links:
-  - name: Mastodon Meta Discussion Board
-    url: https://discourse.joinmastodon.org/
+  - name: GitHub Discussions
+    url: https://github.com/mastodon/mastodon/discussions
     about: Please ask and answer questions here.
+  - name: Bug Bounty Program
+    url: https://app.intigriti.com/programs/mastodon/mastodonio/detail
+    about: Please report security vulnerabilities here.

SECURITY.md

@@ -1,13 +1,19 @@
 # Security Policy
 
+If you believe you've identified a security vulnerability in Mastodon (a bug that allows something to happen that shouldn't be possible), you should submit the report through our [Bug Bounty Program][bug-bounty]. Alternatively, you can reach us at <[email protected]>.
+
+You should *not* report such issues on GitHub or in other public spaces to give us time to publish a fix for the issue without exposing Mastodon's users to increased risk.
+
+## Scope
+
+A "vulnerability in Mastodon" is a vulnerability in the code distributed through our main source code repository on GitHub. Vulnerabilities that are specific to a given installation (e.g. misconfiguration) should be reported to the owner of that installation and not us.
+
 ## Supported Versions
 
 | Version | Supported          |
 | ------- | ------------------ |
-| 3.4.x   | :white_check_mark: |
-| 3.3.x   | :white_check_mark: |
-| < 3.3   | :x:                |
-
-## Reporting a Vulnerability
+| 3.4.x   | Yes                |
+| 3.3.x   | Yes                |
+| < 3.3   | No                 |
 
-[email protected]
+[bug-bounty]: https://app.intigriti.com/programs/mastodon/mastodonio/detail