[Documentation:Developer] Add testing guide for external devs (#670)

Added a page under testing to explain to process of running workflows as
an external contributor

---------

Co-authored-by: Barb Cutler <[email protected]>
Co-authored-by: Barb Cutler <Barb Cutler>

Author: lavalleeale

_docs/developer/testing/autograding_integration_tests.md

@@ -1,6 +1,6 @@
 ---
 title: Autograding Tests
-category: Developer
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 _NOTE: Currently, these tests can only be run from within Vagrant._

_docs/developer/testing/cypress.md

@@ -1,5 +1,6 @@
 ---
 title: End-to-End testing with Cypress
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 The _End-to-End Testing_ (e2e) suite utilizes [Cypress](https://www.cypress.io/),

_docs/developer/testing/external_contributors.md

@@ -0,0 +1,26 @@
+---
+title: External Contributors
+category: Developer > Development Instructions > Continuous Integration Testing
+---
+
+To run all Submitty workflows on a forked repository, you must manually trigger the workflow. This is because GitHub Actions do not run on forked repositories by default. One of the people in the Submitty organization must manually trigger the workflow for you. To avoid this, you can trust the workflow in your forked repository. This will allow GitHub Actions to run on your forked repository without manual intervention.
+
+---
+
+## Steps for External Contributors
+
+1. The first step is to visit [https://github.com/GITHUB_USERNAME/Submitty/actions](https://github.com/GITHUB_USERNAME/Submitty/actions) (or click the actions tab from your forked submitty repository) and click on the button labeled "I understand my workflows, go ahead and enable them".
+   ![GitHub UI to trust workflows in fork](/images/testing/fork_trust.png)
+
+2. After that, on the left side of the page, click on the workflow labeled "CI" to be able to run the workflow. Then, in the "Run workflow" dropdown, select the branch you want to run the workflow on and click the green "Run workflow" button.
+   ![GitHub UI to manually trigger workflow](/images/testing/fork_dispatch.png)
+3. Congratulations! You have successfully triggered the workflow on your forked repository. You should now see a new started workflow in the list of workflows.
+   ![GitHub UI to view workflow run](/images/testing/fork_workflow_run.png)
+
+---
+
+These steps are drawn from:
+
+[https://github.com/github/docs/issues/15761](https://github.com/github/docs/issues/15761)
+
+[https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-workflow-runs/manually-running-a-workflow](https://docs.github.com/en/actions/managing-workflow-runs-and-deployments/managing-workflow-runs/manually-running-a-workflow)

_docs/developer/testing/github_actions.md

@@ -1,5 +1,6 @@
 ---
 title: GitHub Actions
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 We utilize [GitHub actions](https://docs.github.com/en/actions) to enable *continuous integration*

_docs/developer/testing/index.md

@@ -1,5 +1,6 @@
 ---
-title: Testing
+title: Continuous Integration Testing
+category: Developer > Development Instructions
 ---
 
 To verify expected behavior of Submitty, we use

_docs/developer/testing/install_php.md

@@ -1,5 +1,6 @@
 ---
 title: Install PHP
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 In order to run the PHP Linter, Static Analysis, and PHPUnit tests locally 

_docs/developer/testing/linting_static_analysis.md

@@ -1,5 +1,6 @@
 ---
 title: Linting / Static Analysis
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 To ensure the [Coding Standards](/developer/coding_style_guide) of Submitty, we use a mixture

_docs/developer/testing/php_unit_tests.md

@@ -1,5 +1,6 @@
 ---
 title: PHP Unit Tests
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 To validate the unit behavior of the site code, we utilize 

_docs/developer/testing/python_unit_tests.md

@@ -1,5 +1,6 @@
 ---
 title: Python Unit Tests
+category: Developer > Development Instructions > Continuous Integration Testing
 ---
 
 The following Python modules of Submitty are unit tested:

images/testing/fork_dispatch.png

@@ -214,6 +214,7 @@ var NAVTREE =
                 [ "Localization / Language Support", "/developer/development_instructions/localization", null ],
                 [ "Continuous Integration Testing", "/developer/testing/index", [
                     [ "Overview", "/developer/testing/index", null ],
+                    ["External Contributors", "/developer/testing/external_contributors", null],
                     [ "Installing PHP", "/developer/testing/install_php", null ],
                     [ "Linting / Static Analysis", "/developer/testing/linting_static_analysis", null ],
                     [ "Python Unit Tests", "/developer/testing/python_unit_tests", null ],