Rename type definition files. Update documentation. Update date-fn functions being used.

types/Stickers.d.ts

@@ -0,0 +1,24 @@
+type StickerVal = -2 | -1 | 0 | 1 | 2 | null;
+
+type ValidStickerVal = -2 | -1 | 0 | 1 | 2;
+
+interface AddEditStickerProps {
+  date: Date;
+  sticker: ValidStickerVal;
+}
+
+interface Sticker {
+  id: string;
+  date: string;
+  sticker: StickerVal;
+  edited: boolean;
+  manual: boolean;
+}
+
+type StickerDays = Sticker[];
+
+interface StickerModal {
+  isOpen: boolean;
+  selectedSticker: StickerVal;
+  step: number;
+}