Add network security config to allow user certs on Android

(Original commit by James Harvey (@jmshrv) on 2023-10-26 in 8bf1f1c)

android/app/src/main/AndroidManifest.xml

@@ -9,7 +9,7 @@
          In most cases you can leave this as-is, but you if you want to provide
          additional functionality it is fine to subclass or reimplement
          FlutterApplication and put your custom class here. -->
-  <application android:name="${applicationName}" android:label="Finamp" android:icon="@mipmap/ic_launcher" android:usesCleartextTraffic="true" android:requestLegacyExternalStorage="true" android:allowBackup="false" android:fullBackupContent="false">
+  <application android:name="${applicationName}" android:label="Finamp" android:icon="@mipmap/ic_launcher" android:usesCleartextTraffic="true" android:requestLegacyExternalStorage="true" android:allowBackup="false" android:fullBackupContent="false" android:networkSecurityConfig="@xml/network_security_config">
     <activity android:name="com.ryanheise.audioservice.AudioServiceActivity" android:launchMode="singleTop" android:theme="@style/LaunchTheme" android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode" android:hardwareAccelerated="true" android:windowSoftInputMode="adjustResize" android:exported="true">
       <!-- Specifies an Android theme to apply to this Activity as soon as
                  the Android process has started. This theme is visible to the user

android/app/src/main/res/xml/network_security_config.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<network-security-config>
+    <base-config cleartextTrafficPermitted="true">
+        <trust-anchors>
+            <certificates src="system" />
+            <certificates src="user" />
+        </trust-anchors>
+    </base-config>
+</network-security-config>