Turn hardcoded strings into constants to resolve #4

src/constants.rs

@@ -0,0 +1,11 @@
+pub const APP_TITLE: &str = "AntiDrift";
+pub const INTENTION_TITLE: &str = "Intention";
+pub const DURATION_TITLE: &str = "Duration";
+pub const PREVIOUS_SESSIONS_TITLE: &str = "Previous Sessions";
+pub const SESSION_STATS_TITLE: &str = "Session Stats";
+pub const STATUS_TITLE: &str = "Status";
+pub const PROVIDE_INTENTION: &str = "Provide intention! ";
+pub const PROVIDE_VALID_DURATION: &str = "Provide valid duration in minutes! ";
+pub const READY_TO_START: &str = "Ready to start next session.";
+pub const SESSION_IN_PROGRESS: &str = "Session In-Progress";
+pub const RATE_TITLES: &str = "Press 1, 2, 3 to rate titles!";