Clarify public instance rules and definition of analytics (#565)

* Add section 'Rules for public instances'

* Clarify that all external scripts are prohibited

* Rename section 'Rules to have your instance in this list:'

* Update link to rules in new instance proposal

* Don't change the title, since public instances can also not be in the list

---------

Co-authored-by: TheFrenchGhosty <47571719+TheFrenchGhosty@users.noreply.github.com>

.github/ISSUE_TEMPLATE/new_instance.yaml

@@ -44,7 +44,7 @@ body:
         required: true
       - label: "If dash, proxy + download is enabled (default settings), the instance has unlimited traffic/bandwidth or close to unlimited (100TB minimum)"
         required: true
-      - label: "Instance is not running any kind of analytics"
+      - label: "Instance is not running any kind of analytics, including external scripts of any kind"
         required: true
       - label: "If using Cloudflare or any other DDoS protection service, settings are configured to allow uptime monitoring. Cloudflare users can consult [this](https://updown.io/doc/known-issues-when-monitoring-a-cloudflare-protected-website) guide"
         required: true
@@ -60,6 +60,14 @@ body:
       - label: "Ensure a proper uptime of my instance (around 90%)"
         required: true
 
+  - type: checkboxes
+    attributes:
+      label: Rules for public instances
+      description: By submitting this proposal, you agree to follow the [rules for public instances](https://docs.invidious.io/instances/#rules-for-public-instances). 
+      options:
+        - label: I agree to follow the rules for public instances
+          required: true
+
   - type: input
     id: country
     attributes: