Fix Chromecast setup

[MattiasBuelens]

The ChromecastButton wasn't working correctly:

• It didn't show up automatically, even when there are Chromecast receivers available on the Wi-Fi network.
• When starting to cast, the app crashed with the following error:

  java.lang.IllegalArgumentException: background can not be translucent: #0
    at androidx.core.graphics.ColorUtils.calculateContrast(ColorUtils.java:176)
    at androidx.mediarouter.app.MediaRouterThemeHelper.getControllerColor(MediaRouterThemeHelper.java:179)
    at androidx.mediarouter.app.MediaRouterThemeHelper.getRouterThemeId(MediaRouterThemeHelper.java:314)
    at androidx.mediarouter.app.MediaRouterThemeHelper.createThemedDialogStyle(MediaRouterThemeHelper.java:158)
    at androidx.mediarouter.app.MediaRouteChooserDialog.<init>(MediaRouteChooserDialog.java:142)

This PR fixes these issues, and makes Chromecast work out-of-the-box in our demo app. I also added a new guide explaining how to do this in your own app.

Thanks @ceyhun-o for reporting!

[m-derakhshan]

@MattiasBuelens Hello, Thank you for addressing this request quickly. May I kindly ask for a deployment so we can use it in our app?

[MattiasBuelens]

@m-derakhshan We're going to fix #35 first, since otherwise Chromecast is still not very usable. But expect a new release soon. 😉

[MattiasBuelens]

@m-derakhshan Fix is in 1.7.3. 🚀

[m-derakhshan]

@MattiasBuelens oh thank you. that was fast :)