Improve location permission request and description

app/src/main/java/io/nekohasekai/sfa/ktx/Context.kt

@@ -0,0 +1,9 @@
+package io.nekohasekai.sfa.ktx
+
+import android.content.Context
+import android.content.pm.PackageManager
+import androidx.core.content.ContextCompat
+
+fun Context.hasPermission(permission: String): Boolean {
+    return ContextCompat.checkSelfPermission(this, permission) == PackageManager.PERMISSION_GRANTED
+}