Add automatic MEX compilation entry

Author: korbinian90

docs/development/compilation/index.md

@@ -19,3 +19,18 @@ Platform-specific throubleshooting is available with the links above. We list he
 !!! failure "`bad image handle dimensions` error"
 
     The error "`bad image handle dimensions`" when trying to display an image is an indication that the MEX files are not compatible with your platform and should be recompiled.
+
+## Automatic recompilation on GitHub Actions
+
+!!! info "How is the recompilation triggered?"
+
+    If new c files or changes are pushed to main, the [compile MEX](https://github.com/spm/spm/actions/workflows/compile_mex.yml) action will automatically run and recompile all MEX files. In can also be triggered manually, which works for a any branch.
+
+The compiled MEX files will be available as zip a file under the [compile MEX](https://github.com/spm/spm/actions/workflows/compile_mex.yml) action by selecting the corresponding run of the action and downloading the spm-mex-all.zip file. It contains compiled MEX files for Windows, Linux, MacOS (Intel) and MacOS (Apple Silicon).
+
+The suggested steps after changing or adding new c code is:
+1. Confirm that the [automatic tests](https://github.com/spm/spm/actions/workflows/matlab.yml) still succeed
+2. Download the [automatically compiled MEX files](https://github.com/spm/spm/actions/workflows/compile_mex.yml)
+3. Manually add the MEX files of the corresponding change to the SPM repository (.mexa64, .mexmaca64, .mexmaci64, .mexw64)
+
+Note: Currently, the action doesn't compile the external c dependencies. This is because of a problem of compiling the fieldtrip dependency on windows.