Add Javadoc about path patterns (#3626)

Motivation:

I've missed adding Javadoc before merging the following PR:
#3562

Modifications:

- Add Javadoc to `AbstractBindingBuilder#exclude` and `RouteBuilder#exclude` methods.

core/src/main/java/com/linecorp/armeria/server/AbstractBindingBuilder.java

@@ -409,6 +409,8 @@ public AbstractBindingBuilder addRoute(Route route) {
     /**
      * Adds a {@code pathPattern} that is supposed to be excluded from the {@link Route}s built by this
      * {@link AbstractBindingBuilder}.
+     * Please refer to <a href="https://armeria.dev/docs/server-basics#path-patterns">Path patterns</a>
+     * to learn more about path pattern syntax.
      */
     public AbstractBindingBuilder exclude(String pathPattern) {
         requireNonNull(pathPattern, "pathPattern");
@@ -475,4 +477,3 @@ final List<Route> buildRouteList(Collection<Route> fallbackRoutes) {
         return builder.build();
     }
 }
-

core/src/main/java/com/linecorp/armeria/server/RouteBuilder.java

@@ -435,6 +435,8 @@ RouteBuilder fallback(boolean isFallback) {
     /**
      * Adds a {@code pathPattern} that is supposed to be excluded from the {@link Route} built by this
      * {@link RouteBuilder}.
+     * Please refer to <a href="https://armeria.dev/docs/server-basics#path-patterns">Path patterns</a>
+     * to learn more about path pattern syntax.
      */
     RouteBuilder exclude(String pathPattern) {
         requireNonNull(pathPattern, "pathPattern");