feat: Add docs on how to update the dilter back-end

README.md

@@ -15,6 +15,7 @@ _This project has been created by the Wiris Engineering Team and is aimed at Moo
     - [Quick start](#quick-start)
     - [How it works](#how-it-works)
     - [Scripts in action](#scripts-in-action)
+    - [Update the PHP integration](#update-the-php-integration)
     - [Update the DB](#update-the-db)
 - [FAQ](#faq)
 - [Wiris Moodle math & science set](#wiris-moodle-math--science-plugins-set)
@@ -335,6 +336,29 @@ export MOODLE_DOCKER_PHP_VERSION="7.1"
 
 ```
 
+### Update the PHP integration
+
+The [MathType Moodle filter plugin][filter] has a folder in the root called [`integration`](https://github.com/wiris/moodle-filter_wiris/tree/stable/integration) that contains a whole copy of the PHP backend of the MathType Web plugin.
+Ideally, whenever that backend is updated, it should be updated in the filter plugin repository as well.
+This section explains how to do that.
+
+1. Create a branch off the `main` branch of [filter].
+
+2. Replace the `integration` folder with the contents of the PHP backend.
+    The backend can be found, for instance, within any of the compiled plugins with PHP backend found in the GitHub [releases](https://github.com/wiris/plugins/releases) of the [plugins] repository.
+    Extract the plugin and look for the integration folder.
+    For instance, in the case of the `php-ckeditor4` plugin, the integration is the folder `php-ckeditor4-.../ckeditor_wiris/integration`.
+    Replace the `integration` folder in the filter repository with that one.
+    Commit and push.
+
+3. Let the automated Moodle tests pass on the new branch.
+    When they pass correctly, continue.
+
+4. Look for the the `thirdpartylibs.xml` file.
+    Update the `<version>` entry for the `integration` library to be the same as the version of the backend.
+
+5. Open a PR or merge directly to `main`, as appropriate.
+
 ### Update the DB
 
 For each new Moodle version, the database is likely to change. Some times, when we are using an old database, moodle will throw an error and we will have to update it.