Add visibility (#4232)

* Add visibility

* Tab use

* Update app/Models/Days.php

Co-authored-by: Alexandre Alapetite <alexandre@alapetite.fr>

app/Models/Days.php

@@ -1,7 +1,7 @@
 <?php
 
 class FreshRSS_Days {
-	const TODAY = 0;
-	const YESTERDAY = 1;
-	const BEFORE_YESTERDAY = 2;
+	public const TODAY = 0;
+	public const YESTERDAY = 1;
+	public const BEFORE_YESTERDAY = 2;
 }