CI: Ensure Linux version of GDSiON is present for web builds

Since web builds are exported via Linux, it's nice
to have appropriate version available so the
Godot editor doesn't freak out.

Also fix a minor issue in the export plugin.

.github/actions/setup-deps/action.yml

@@ -25,3 +25,13 @@ runs:
       run: |
         curl -JLO ${{ env.GDSION_PATH }}
         unzip libgdsion-${{ inputs.platform }}.zip
+    
+    # Web platform is exported via Linux, so install that version of GDSiON as well.
+    - name: Install GDSiON Linux (Web)
+      if: ${{ inputs.platform == 'web' }}
+      shell: bash
+      env:
+        GDSION_PATH: https://github.com/YuriSizov/gdsion/releases/download/${{ inputs.gdsion-version }}/libgdsion-linux.zip
+      run: |
+        curl -JLO ${{ env.GDSION_PATH }}
+        unzip -n libgdsion-linux.zip

addons/bosca_exports/plugin.gd

@@ -20,4 +20,3 @@ func _enter_tree() -> void:
 func _exit_tree() -> void:
 	if is_instance_valid(_export_plugin_web):
 		remove_export_plugin(_export_plugin_web)
-		_export_plugin_web.free()