Small balance updates and compatibility fix

Largest fix was to address an issue where damage numbers were not working for certain users.  Apparently Instancing isn't fully supported on all browsers!  I have updated the damage number rendering to use a non-instanced strategy instead, and in fact it might even be faster/simpler than the previous solution!  Damage numbers was one of the areas where I actually ended up not using regular SpriteRenderers, since they are spawned/destroyed so frequently that it ended up having a major performance impact (especially if I tried to use TMP components!).  New solution uses a pre-baked mesh of 512 digit quads, and a 512x2 texture that controls their positions/color/glyph.  

Additionally there have been minor balance changes

• Decreased health of The Slime King to be a little more kind towards players who built many Bomb towers in chapter 1
• Decreased health of several waves that were slightly too high difficulty relative to neighboring waves

Brainstorming some sort of recovery mechanic to help out players that are getting stuck with a layout that doesn't work for a specific wave, to allow them to keep progressing.  Of course lowering the difficulty is always possible, but in general people don't like to do that for a single wave.  Instead, I wonder if there could be some sort of 1-time option to duplicate a tower.  The power would scale as you level up your towers, as your towers are more powerful and so more useful to duplicate.  And the ending screen could still give you a nice rewarding callout if you manage to complete the game without activating any of the duplications.