Update PR template and contributing guide

.github/CONTRIBUTING.md

@@ -18,8 +18,10 @@ Interested in contributing? Awesome!
   - [Server side](#server-side)
   - [Client side](#client-side)
   - [Client and server side](#client-and-server-side)
-  - [Testing the federation of PeerTube servers](#testing-the-federation-of-peertube-servers)
+  - [RTL layout](#rtl-layout)
+  - [Testing](#testing)
     - [Unit tests](#unit-tests)
+    - [Testing the federation of PeerTube servers](#testing-the-federation-of-peertube-servers)
   - [Emails](#emails)
 - [Plugins & Themes](#plugins--themes)
 
@@ -224,14 +226,16 @@ $ createdb -O peertube peertube_test{1,2,3}
 Build the application and flush the old tests data:
 
 ```
-$ npm run build -- --light
+$ npm run build
 $ npm run clean:server:test
 ```
 
-This will run 3 nodes:
+To run 3 nodes:
 
 ```
-$ npm run play
+$ NODE_APP_INSTANCE=1 NODE_ENV=test npm start
+$ NODE_APP_INSTANCE=2 NODE_ENV=test npm start
+$ NODE_APP_INSTANCE=3 NODE_ENV=test npm start
 ```
 
 Then you will get access to the three nodes at `http://localhost:900{1,2,3}`

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,24 +6,16 @@
 
 <!-- If suggesting a new feature or change, please discuss it in an issue first -->
 <!-- If fixing a bug, there should be an issue describing it with steps to reproduce -->
-<!-- start with closing keywords if any apply: https://docs.github.com/en/enterprise/2.16/user/github/managing-your-work-on-github/closing-issues-using-keywords -->
 
 ## Has this been tested?
 
-<!--- Put an `x` in the box that applies: -->
+<!-- Put an `x` in the box that applies: -->
+<!-- Check the unit test guide: https://docs.joinpeertube.org/contribute-getting-started?id=unit-tests -->
+
 - [ ] 👍 yes, I added tests to the test suite
-- [ ] 👍 yes, light tests as follows are enough
 - [ ] 💭 no, because this PR is a draft and still needs work
-- [ ] 🙅 no, because they aren't needed
-- [ ] 🙋 no, because I need help
-
-<!--
-If you didn't test via unit-testing, you will still be asked to prove your fix is effective, doesn't have side-effects, or that your feature simply works:
-
-Please describe the tests that you ran to verify your changes.
-Provide instructions so we can reproduce.
-Please also list any relevant details for your test configuration(s):
--->
+- [ ] 🙅 no, because this PR does not update server code
+- [ ] 🙋 no, because I need help <!-- Detail how we can help you >
 
 ## Screenshots