Added more property help docs

app/private/docs/property/damage.md

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+# Damage
+
+Damage can be applied by an action to damage a target creature's [health bars](/docs/property/attribute). The damage will be modified by [damage multipliers](/docs/property/damage-multiplier), which apply vulnerability, resistance, and immunity before the damage is applied.
+
+---
+
+### Damage
+
+A [computed field](/docs/computed-fields) that determines how much damage to do to the target creature.
+
+### Damage type
+
+Damage type determines how the damage is treated by [damage multipliers](/docs/property/damage-multiplier). A custom type can be used, or one of the existing types can be selected.
+
+There are two special damage types:
+
+**Extra damage** Damage with the `extra` type will take on the damage type of whatever damage was applied before it by an action. So if an action deals 12 `piercing` damage and `3` extra damage, it will instead deal 15 `piercing` damage.
+
+**Healing** Damage with the `healing` type will heal a creature instead of damaging them.
+
+### Target
+
+- **Target** Apply the damage to the target of the action
+- **Self** Apply the damage to the creature taking the action
+
+### Tags
+
+See [Tags](/docs/tags)
+
+### Don't show in log
+
+If set, the damage will be applied but not show in the log.