fix(android): add space between default useragent and custom AppendUs…

…erAgent (#861)

cordova-android adds a space between the default user agent and the custom one:
https://github.com/apache/cordova-android/blob/c144c0811249e22f91253ef919cc767f892a8fdf/framework/src/org/apache/cordova/engine/SystemWebViewEngine.java#L214

With this change cordova-androids and the IAB user agent are exactly the same.

src/android/InAppBrowser.java

@@ -970,7 +970,7 @@ public void postMessage(String data) {
                     settings.setUserAgentString(overrideUserAgent);
                 }
                 if (appendUserAgent != null) {
-                    settings.setUserAgentString(settings.getUserAgentString() + appendUserAgent);
+                    settings.setUserAgentString(settings.getUserAgentString() + " " + appendUserAgent);
                 }
 
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