Added submodule for external data storage (#755)

* Added submodule for external data storage

* added contributing page to describe submodule

Author: Josef-Haupt

.github/workflows/ci.yml

@@ -22,6 +22,8 @@ jobs:
         python-version: ["3.11"]
     steps:
       - uses: actions/checkout@v4
+        with:
+          submodules: true
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5
         with:

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "tests/data"]
+	path = tests/data
+	url = https://github.com/birdnet-team/birdnet-test-data.git

CONTRIBUTING.md

@@ -0,0 +1,30 @@
+### Testdata (optional)
+
+This project uses a submodule for its testdata.
+
+If you want to run the tests locally you need to initialize the submodule:
+
+```bash
+git submodule update --init --recursive
+```
+
+Or checkout the submodule during cloning:
+
+```bash
+git clone --recurse-submodules https://github.com/birdnet-team/BirdNET-Analyzer.git
+```
+
+If the testdata has changed and you want to update the repo to use the new current testdata follow these steps:
+
+```bash
+cd tests/data
+git pull origin main
+cd ..
+git add data
+git commit -m "Update testdata"
+git push
+```
+
+This will set up the repo to use the current ref of the submodule.
+
+**Note**: If you wan to add data you do so by either checking out the submodule as a regular repo and just add-commit-push from there or use the subdirectory containing the submodule like a regular git repository (don't forget to manually update the ref in the main repo)