add macroable docs

packages/macroable.md

@@ -31,13 +31,26 @@ const { Macroable } = require('@supercharge/macroable')
 
 
 ## Traditional Approach
+The typical approach extending a JavaScript class is applying a custom function to the class’ prototype. This adds the given function to the class and makes it callablel on class instances. Here’s how you would do it:
+
+```ts
+class User {
+  private firstname: string = 'Supercharge'
+}
+
+// in another file/package
+User.prototype.greet = function () {
+  return `Hello ${this.firstname}!`
+}
+```
 
 
 ## Using Macroable
-Tba.
+The `Macroable` class is a base class exposing methods to extends a class prototype in a declarative way. We call this declarative way "adding a macro". You may also determine whether a method is macro’ed to the class. Or you can remove all macros from a class.
+
 
 ### Adding Macros
-Tba.
+Add a macro to a class by extending the `Macroable` class and calling the static `Class.macro(name, method)` function:
 
 ```js
 import { Macroable } from '@supercharge/macroable'
@@ -46,6 +59,7 @@ class User extends Macroable {
   private firstname: string = 'Supercharge'
 }
 
+// in another file/package
 User.macro('hello', function () {
   return `Hello ${this.firstname}!`
 })
@@ -58,12 +72,34 @@ user.hello()
 
 
 ### Has Macro
-You can remove all macros from a class using the static `flushMacros` method:
+You may determine whether a function on a class was added as a macro using the `hasMacro` method:
 
 ```ts
 Macroable.hasMacro('method-name')
 ```
 
+Here’s an example of checking whether a class’s method is a macro function:
+
+```ts
+import { Macroable } from '@supercharge/macroable'
+
+class User extends Macroable {
+  greeting(): string {
+    return 'Hello World!'
+  }
+}
+
+User.macro('hello', function () {
+  return `Hello ${this.firstname}!`
+})
+
+User.hasMacro('hello')
+// true
+
+User.hasMacro('greeting')
+// false   -- because "greeting" was not macro’ed to the class
+```
+
 
 ### Deleting Macros
 You can remove all macros from a class using the static `flushMacros` method:
@@ -94,14 +130,16 @@ user.hello
 
 
 ## Adding IntelliSense
-Tba.
+A shortcoming for macros are IntelliSense in your editor. During development you want your editor to show autocompletions while typing. Dynamically adding methods to a class using macros won’t add type definitions to your code.
 
-Use TypeScript interface merging.
+A way to add IntelliSense support is using TypeScript’s interface merging. For example, the `HttpRequest` class in the Supercharge framework is macroable. Any third-party package adding methods to the request can also inject typings using declaration merging. Merge your types by defining a module for the extended package and export the extended interface:
 
 ```ts
 declare module '@supercharge/http' {
-  export class Request {
+  export interface HttpRequest {
     session(): Session
   }
 }
 ```
+
+You should add the extended interface declarations in your typings file (typically a `.d.ts` file) or in one of your package’s exported files.