Update docs and usage

Author: jrosen081

Sources/JavaKit/Macros.swift

@@ -99,10 +99,9 @@ public macro JavaField(_ javaFieldName: String? = nil) = #externalMacro(module:
 /// The macro must be used within a specific JavaClass instance.
 ///
 /// ```swift
-/// @JavaClass("org.swift.example.HelloSwift")
-/// struct HelloSwift {
-///     @JavaField
-///     var counter: Int32
+/// extension JavaClass<HelloSwift> {
+///   @JavaStaticField
+///   var initialValue: Double
 /// }
 /// ```
 @attached(accessor)

Sources/JavaKitExample/JavaKitExample.swift

@@ -103,13 +103,13 @@ struct HelloSwift {
 }
 
 extension JavaClass<HelloSwift> {
-  @JavaField
+  @JavaStaticField
   var initialValue: Double
 }
 
 @JavaClass("com.example.swift.HelloSubclass", extends: HelloSwift.self)
 struct HelloSubclass {
-  @JavaStaticField
+  @JavaField
   var greeting: String
 
   @JavaMethod