core/src/main/java/org/trimou/engine/MustacheEngineBuilder.java
public MustacheEngineBuilder addMustacheListener(
            MustacheListener listener) {
        checkArgumentNotNull(listener);
        checkNotBuilt();
        this.mustacheListeners.add(listener);
        return this;
    }
public MustacheEngineBuilder addMustacheListener(
            MustacheListener listener) {
        checkArgumentNotNull(listener);
        checkNotBuilt();
        this.mustacheListeners.add(listener);
        return this;
    }
Adds a {@link Mustache} listener. Manually added listeners are always
registered before listeners added via configuration extensions.

@param listener
@return self