Partially implement Flower Gift

The Attack and Special Defense boost works, but only for the ability holder currently. It does not change Cherrim's form yet.
Also adds the necessary battler tag entries because I forgot them in the previous commit.

src/data/enums/battler-tag-type.ts

@@ -24,6 +24,8 @@ export enum BattlerTagType {
   THUNDER_CAGE = "THUNDER_CAGE",
   PROTECTED = "PROTECTED",
   KINGS_SHIELD = "KINGS_SHIELD",
+  OBSTRUCT = "OBSTRUCT",
+  SILK_TRAP = "SILK_TRAP",
   BANEFUL_BUNKER = "BANEFUL_BUNKER",
   BURNING_BULWARK = "BURNING_BULWARK",
   ENDURING = "ENDURING",