Adds versioned 0.13.0 docs (#1907)

Author: infomiho

web/docs/_sendingEmailsInDevelopment.md

@@ -0,0 +1,60 @@
+---
+title: Accessing the configuration 
+---
+
+Whenever you start a Wasp app, you are starting two processes.
+ - **The client process** - A React app that implements your app's frontend.
+
+    During development, this is a dev server with hot reloading. In production,
+    it's a simple process that serves pre-built static files with environment variables
+    embedded during the build (details depend on [how you deploy
+    it](/docs/advanced/deployment/overview)).
+
+ - **The server process** - An Express server that implements your app's backend.
+ 
+    During development, this is an Express server controlled by a
+    [`nodemon`](https://www.npmjs.com/package/nodemon) process that takes care of
+    hot reloading and restarts. In production, it's a regular Express server run
+    using Node.
+
+Check [the introduction](/docs) for a more in-depth explanation of Wasp's runtime architecture.
+
+You can configure both processes through environment variables. See [the
+deployment instructions](/docs/advanced/deployment/manually#environment-variables) for a full list
+of supported variables.
+
+Wasp gives you runtime access to the processes' configurations through **configuration objects**.
+
+## Server configuration object
+
+The server configuration object contains these fields:
+
+- `frontendUrl: String` - Set it with env var `WASP_WEB_CLIENT_URL`.
+
+  The URL of your client (the app's frontend).<br/>
+  Wasp automatically sets it during development when you run `wasp start`.<br/>
+  In production, you should set it to your client's URL as the server sees it
+  (i.e., with the DNS and proxies considered).
+
+You can access it like this:
+```js
+import { config } from 'wasp/server'
+
+console.log(config.frontendUrl)
+```
+
+## Client configuration object
+The client configuration object contains these fields:
+- `apiUrl: String` - Set it with env var `REACT_APP_API_URL`
+
+  The URL of your server (the app's backend).<br/>
+  Wasp automatically sets it during development when you run `wasp start`.<br/>
+  In production, it should contain the value of your server's URL as the user's browser
+  sees it (i.e., with the DNS and proxies considered).
+
+You can access it like this:
+```js
+import { config } from 'wasp/client'
+
+console.log(config.apiUrl)
+```