[Scarpet] Added ability to cancel events (#1497)

* Added ability to cancel events

* Made more events cancellable

* Added event_priority to __config

* Check for string values for performance

* Made player_finishes_using_item cancellable

* Made player_chooses_recipe cancellable

* Made player_swaps_hands cancellable

* Made player_message cancellable

* Added __on_player_placing_block (#1498)

* Added event to docs, keywords, event_test

* Added docs for event cancellation

src/main/java/carpet/script/CarpetScriptHost.java

@@ -75,6 +75,7 @@ public class CarpetScriptHost extends ScriptHost
     private Tag globalState;
     private int saveTimeout;
     public boolean persistenceRequired;
+    public double eventPriority;
 
     public Map<Value, Value> appConfig;
     public Map<String, CommandArgument> appArgTypes;
@@ -298,6 +299,7 @@ public class CarpetScriptHost extends ScriptHost
             setPerPlayer(config.getOrDefault(new StringValue("scope"), new StringValue("player")).getString().equalsIgnoreCase("player"));
             persistenceRequired = config.getOrDefault(new StringValue("stay_loaded"), Value.TRUE).getBoolean();
             strict = config.getOrDefault(StringValue.of("strict"), Value.FALSE).getBoolean();
+            eventPriority = config.getOrDefault(new StringValue("event_priority"), Value.ZERO).readDoubleNumber();
             // check requires
             Value loadRequirements = config.get(new StringValue("requires"));
             if (loadRequirements instanceof FunctionValue)