Disable show[Save|Open]FilePicker on Android

Latest Chrome completely broke showSaveFilePicker.
This has caused so many bugs in the past.
Let's just not use it on broken platforms.

Author: GarboMuffin

src/containers/sb3-downloader.jsx

@@ -295,7 +295,9 @@ SB3Downloader.propTypes = {
 };
 SB3Downloader.defaultProps = {
     className: '',
-    showSaveFilePicker: typeof showSaveFilePicker === 'function' ? window.showSaveFilePicker.bind(window) : null
+    showSaveFilePicker: typeof showSaveFilePicker === 'function' && !navigator.userAgent.includes('Android') ?
+        window.showSaveFilePicker.bind(window) :
+        null
 };
 
 const mapStateToProps = state => ({

src/lib/sb-file-uploader-hoc.jsx

@@ -288,7 +288,9 @@ const SBFileUploaderHOC = function (WrappedComponent) {
         onSetFileHandle: PropTypes.func
     };
     SBFileUploaderComponent.defaultProps = {
-        showOpenFilePicker: typeof showOpenFilePicker === 'function' ? window.showOpenFilePicker.bind(window) : null
+        showOpenFilePicker: typeof showOpenFilePicker === 'function' && !navigator.userAgent.includes('Android') ?
+            window.showOpenFilePicker.bind(window) :
+            null
     };
     const mapStateToProps = (state, ownProps) => {
         const loadingState = state.scratchGui.projectState.loadingState;