chore(readme): improve readme w/ additional details for custom configurations

improve readme w/ additional details for custom configurations

Author: danbucholtz

README.md

@@ -51,19 +51,20 @@ npm run build
 ```
 
 
-## Custom Config Files
+## Custom Configuration
 
-In many cases, the defaults which Ionic provides covers most of the scenarios required by developers. However, Ionic App Scripts does provide multiple ways to configure and override the defaults for each of the various tasks. Note that Ionic will always apply its defaults for any property that was not provided by custom configurations.
+In many cases, the defaults which Ionic provides covers most of the scenarios required by developers. However, Ionic App Scripts does provide multiple ways to configure and override the defaults for each of the various tasks. Note that Ionic will always apply its defaults for any property that was not provided by custom configuration.
 
 [Default Config Files](https://github.com/driftyco/ionic-app-scripts/tree/master/config)
 
 ### package.json Config
 
-Within the `package.json` file, there's also a handy [config](https://docs.npmjs.com/misc/config#per-package-config-settings) property which can be used. Below is an example of setting a custom config file using the `config` property in a project's `package.json`.
+Ionic projects use the `package.json` file for configuration. There's a handy [config](https://docs.npmjs.com/misc/config#per-package-config-settings) property which can be used. Below is an example of setting a custom config file using the `config` property in a project's `package.json`.
 
 ```
   "config": {
-    "ionic_rollup": "./config/rollup.config.js",
+    "ionic_bundler": "rollup",
+    "ionic_source_map": "source-map",
     "ionic_cleancss": "./config/cleancss.config.js"
   },
 ```
@@ -103,14 +104,15 @@ npm run build --rollup ./config/rollup.config.js
 
 ### Overriding Config Values
 
-| Config Values   | package.json Config | Cmd-line Flag | Defaults        |
-|-----------------|---------------------|---------------|-----------------|
-| bundler         | `ionic_bundler`     | `--bundler`   | `webpack`       |
-| source map type | `ionic_source_map`  | `--sourceMap` | `eval`          |
-| root directory  | `ionic_root_dir`    | `--rootDir`   | `process.cwd()` |
-| tmp directory   | `ionic_tmp_dir`     | `--tmpDir`    | `.tmp`          |
-| www directory   | `ionic_www_dir`     | `--wwwDir`    | `www`           |
-| build directory | `ionic_build_dir`   | `--buildDir`  | `build`         |
+| Config Values   | package.json Config | Cmd-line Flag | Defaults        | Details        |
+|-----------------|---------------------|---------------|-----------------|----------------|
+| bundler         | `ionic_bundler`     | `--bundler`   | `webpack`       | Chooses which bundler to use: `webpack` or `rollup` |
+| source map type | `ionic_source_map`  | `--sourceMap` | `eval`          | Chooses the webpack `devtool` option. We recommend `eval` or `source-map` |
+| root directory  | `ionic_root_dir`    | `--rootDir`   | `process.cwd()` | The directory path of the Ionic app |
+| tmp directory   | `ionic_tmp_dir`     | `--tmpDir`    | `.tmp`          | A temporary directory for codegen'd files using the Angular `ngc` AoT compiler |
+| src directory   | `ionic_src_dir`     | `--srcDir`    | `src`           | The directory holding the Ionic src code |
+| www directory   | `ionic_www_dir`     | `--wwwDir`    | `www`           | The deployable directory containing everything needed to run the app |
+| build directory | `ionic_build_dir`   | `--buildDir`  | `build`         | The build process uses this directory to store generated files, etc |
 
 
 ### Ionic Environment Variables
@@ -126,6 +128,7 @@ These environment variables are automatically set to [Node's `process.env`](http
 | `IONIC_WWW_DIR`         | The absolute path to the app's public distribution directory.        |
 | `IONIC_BUILD_DIR`       | The absolute path to the app's bundled js and css files.             |
 | `IONIC_APP_SCRIPTS_DIR` | The absolute path to the `@ionic/app-scripts` node_module directory. |
+| `IONIC_SOURCE_MAP`      | The Webpack `devtool` setting. We recommend `eval` or `source-map`.  |
 
 The `process.env.IONIC_ENV` environment variable can be used to test whether it is a `prod` or `dev` build, which automatically gets set by any command. By default the `build` task is `prod`, and the `watch` and `serve` tasks are `dev`. Additionally, using the `--dev` command line flag will force the build to use `dev`.
 
@@ -175,10 +178,10 @@ Example NPM Script:
 - [CleanCss](https://github.com/jakubpawlowicz/clean-css)
 - [TSLint](http://palantir.github.io/tslint/)
 
-
-
 ## Contributing
 
+We welcome any PRs, issues, and feedback! Please be respectful and follow the [Code of Conduct]().
+
 ### Publish a release
 
 Execute the following steps to publish a release: