feat(xanthous): Add configurable natural attacks

Allow configuring the natural attacks (eg, part of their body rather
than an item) of a creature. Each attack has a description and a damage
associated with it.

Change-Id: I69698a8ac4ee2da91e4c88e419593627519522a5
Reviewed-on: https://cl.tvl.fyi/c/depot/+/3220
Reviewed-by: grfn <grfn@gws.fyi>
Tested-by: BuildkiteCI

users/grfn/xanthous/src/Xanthous/Messages.hs

@@ -9,6 +9,7 @@ module Xanthous.Messages
     -- * Game messages
   , messages
   , render
+  , render_
   , lookup
   , message
   , message_
@@ -17,7 +18,7 @@ module Xanthous.Messages
 import Xanthous.Prelude hiding (lookup)
 --------------------------------------------------------------------------------
 import           Control.Monad.Random.Class (MonadRandom)
-import           Data.Aeson (FromJSON, ToJSON, toJSON)
+import           Data.Aeson (FromJSON, ToJSON, toJSON, object)
 import qualified Data.Aeson as JSON
 import           Data.Aeson.Generic.DerivingVia
 import           Data.FileEmbed
@@ -89,6 +90,10 @@ render msg params = do
   tpl <- resolve msg
   pure . toStrict . renderMustache tpl $ toJSON params
 
+-- | Render a message with an empty set of params
+render_ :: (MonadRandom m) => Message -> m Text
+render_ msg = render msg $ object []
+
 lookup :: [Text] -> Message
 lookup path = fromMaybe notFound $ messages ^? ix path
   where notFound