Add mixin support and example mixin

src/main/resources/META-INF/mods.toml

@@ -41,6 +41,8 @@ authors="${mod_authors}" #optional
 # IMPORTANT NOTE: this is NOT an instruction as to which environments (CLIENT or DEDICATED SERVER) your mod loads on. Your mod should load (and maybe do nothing!) whereever it finds itself.
 #displayTest="MATCH_VERSION" # if nothing is specified, MATCH_VERSION is the default when clientSideOnly=false, otherwise IGNORE_ALL_VERSION when clientSideOnly=true (#optional)
 
+mixinConfig = "contraptionsaresafe.mixins.json"
+
 # Access Transformers
 # Optional, if not specified Forge will attempt to find the default META-INF/accesstransformer.cfg and silently continue if not found. May default to an empty list in a future MC.
 # If you specify AT path strings in this list, Forge will attempt to load each of them and throw errors for any that aren't found.