feat: explicitly enable the share-button in Chrome Custom Tabs (#4223)

Chrome defaults to showing it anyways, but Firefox doesn't. By enabling
this feature, users across both browsers will now have the same
experience.

closes tuskyapp/Tusky/issues/4137

app/src/main/java/com/keylesspalace/tusky/util/LinkHelper.kt

@@ -350,6 +350,7 @@ fun openLinkInCustomTab(uri: Uri, context: Context) {
         .build()
     val customTabsIntent = CustomTabsIntent.Builder()
         .setDefaultColorSchemeParams(colorSchemeParams)
+        .setShareState(CustomTabsIntent.SHARE_STATE_ON)
         .setShowTitle(true)
         .build()