Add source documentation to javadocs and add dependency tab (#3917)

Get the most out of javadocs

Bukkit/build.gradle.kts

@@ -105,6 +105,10 @@ tasks {
         opt.links("https://jd.adventure.kyori.net/api/4.9.3/")
         opt.links("https://google.github.io/guice/api-docs/" + libs.guice.get().versionConstraint.toString() + "/javadoc/")
         opt.links("https://checkerframework.org/api/")
+        opt.isLinkSource = true
+        opt.bottom(File("$rootDir/javadocfooter.html").readText())
+        opt.isUse = true
         opt.encoding("UTF-8")
+        opt.keyWords()
     }
 }