add a List extension for determining Mimetype of multiple uris

commons/src/main/kotlin/com/simplemobiletools/commons/extensions/List.kt

@@ -0,0 +1,24 @@
+package com.simplemobiletools.commons.extensions
+
+import android.net.Uri
+import java.util.*
+
+fun List<Uri>.getMimeType(): String {
+    val mimeGroups = HashSet<String>(size)
+    val subtypes = HashSet<String>(size)
+    forEach {
+        val parts = it.path.getMimeTypeFromPath().split("/")
+        if (parts.size == 2) {
+            mimeGroups.add(parts.getOrElse(0, { "" }))
+            subtypes.add(parts.getOrElse(1, { "" }))
+        } else {
+            return "*/*"
+        }
+    }
+
+    return when {
+        subtypes.size == 1 -> "${mimeGroups.first()}/${subtypes.first()}"
+        mimeGroups.size == 1 -> "${mimeGroups.first()}/*"
+        else -> "*/*"
+    }
+}