docs: basic kit info (#206)

docs/content/4.modules/1.intro.md

@@ -1 +1,8 @@
 # Nuxt Modules
+
+Nuxt modules allow encapsulating features and detailed customization of how Nuxt works. You can use them to add features simply within your own project, or publish a library for others to use.
+
+You can browse through a list of community-provided Nuxt modules at [modules.nuxtjs.org](https://modules.nuxtjs.org/), or via [GitHub discovery](https://github.com/topics/nuxt-module)
+
+**Note**:
+Not all current Nuxt modules are compatible with Nuxt3, in particular modules that have a runtime component. Module authors should consult [the documentation on creating compatible modules](/modules/kit), and please feel free to file an issue on the module repository to track progress.

docs/content/4.modules/2.kit.md

@@ -1 +1,83 @@
-# Kit (advanced)
+# Creating Modules
+
+Nuxt provides helper functions (accessed from `@nuxt/kit`) to assist in creating modules that can run on both Nuxt 2 and Nuxt 3.
+
+```js
+import { defineNuxtModule } from '@nuxt/kit'
+
+export default defineNuxtModule({
+  // The npm package name of your module
+  name: '@nuxtjs/sample-module',
+  // The key in `nuxt.config` that holds your module options
+  configKey: 'sample',
+  // Default configuration options for your module
+  defaults: {},
+  hooks: {},
+  setup (options, nuxt) {},
+})
+```
+
+## Module options
+
+Nuxt will automatically merge the configuration provided to your module (whether passed directly inline or in a configuration section in `nuxt.config`) with the defaults you provide.
+
+```js
+export default {
+  buildModules: [
+    ['@nuxtjs/sample-module', { sampleOption: true }]
+  ],
+  sample: {
+    anotherOption: 42
+  }
+}
+```
+
+## Hooks
+
+For simple modules, you may be able to implement all you need simply with several hooks in this section.
+
+## Setup
+
+If the `hooks` configuration is not enough, you can provide a full setup function, with access to `nuxt`. You will no longer have access to `this` as in the previous Nuxt module specification, but there are dedicated helper functions from `@nuxt/kit` to replace the module container methods from previously.
+
+```js
+import { defineNuxtModule, addPlugin } from '@nuxt/kit'
+
+export default defineNuxtModule({
+  // ...
+  setup (options, nuxt) {
+    addPlugin({
+      src: path.resolve(__dirname, 'templates/foo.js')
+    })
+  },
+})
+```
+
+## Advanced usage
+
+In some cases you may need access to the Nuxt instance in order to define your module, for example, using other Nuxt options:
+
+```js
+import { defineNuxtModule } from '@nuxt/kit'
+
+export default defineNuxtModule(nuxt => ({
+  // ...
+  defaults: {
+    root: nuxt.options.rootDir
+  },
+}))
+```
+
+## Module helpers
+
+A number of helpers are also provided for use within this context (with more coming - feature requests welcome) that ensure compatible behavior across Nuxt versions.
+
+* addTemplate
+* addErrorLayout
+* addLayout
+* addPlugin
+* addServerMiddleware
+* extendBuild
+* extendRoutes
+
+Each of these functions provides documentation via IDE hover/autocomplete.