Bring back the "tint secret doors" feature (resolves #7)

This partially reverts commit 42529d3df6.

src/features/highlight_secret_doors.js

@@ -0,0 +1,34 @@
+import {settingsKey} from "../settings.js"
+
+const SECRET_DOOR_TINT = 0x888888
+
+// Tint all secret doors dark grey
+export function onCanvasReady(currentCanvas) {
+	if (game.settings.get(settingsKey, "highlightSecretDoors")) {
+		const types = CONST.WALL_DOOR_TYPES
+		const secretDoors = canvas.controls.doors.children.filter(control => control.wall.data.door == types.SECRET)
+		secretDoors.forEach(control => control.icon.tint = SECRET_DOOR_TINT)
+	}
+}
+
+// If door type has been changed, tint the door accordingly
+export function onUpdateWall(scene, wall, update) {
+	if (!game.settings.get(settingsKey, "highlightSecretDoors"))
+		return
+	const types = CONST.WALL_DOOR_TYPES
+	if (wall.door === types.NONE)
+		return
+	// Find the door control corresponding to the changed door
+	const changedDoor = canvas.controls.doors.children.find(control => control.wall.data._id === wall._id);
+	// If the changed door doesn't have a control it's not on this scene - ignore it
+	if (!changedDoor)
+		return
+	// The wall object we got passed might be from another scene so we replace it with the door from the current scene
+	wall = changedDoor.wall.data
+	if (wall.door === types.DOOR)
+		changedDoor.icon.tint = 0xFFFFFF
+	else if (wall.door === types.SECRET)
+		changedDoor.icon.tint = SECRET_DOOR_TINT
+	else
+		console.warn("Smart Doors | Encountered unknown door type " + wall.door + " while highlighting secret doors.")
+}