docs: better start and stop examples (#1521)

This PR adds separate examples for each of the different methods of starting/stopping a node (promises, callbacks, events) instead of a single confusing example with all the methods in one code snippet.

This makes for easier copy/paste.

Also switches promise method to use async/await syntax.

License: MIT
Signed-off-by: Alan Shaw <alan@tableflip.io>

Author: alanshaw

README.md

@@ -355,35 +355,55 @@ Start listening for connections with other IPFS nodes on the network. In most ca
 This method is asynchronous. There are several ways to be notified when the node has finished starting:
 
 1. If you call `node.start()` with no arguments, it returns a promise.
-2. If you pass a function as the final argument, it will be called when the node is started. *(Note: this method will **not** return a promise if you use a callback function.)*
+
+    ```js
+    const node = new IPFS({ start: false })
+
+    node.on('ready', async () => {
+      console.log('Node is ready to use!')
+
+      try {
+        await node.start()
+        console.log('Node started!')
+      } catch (error) {
+        console.error('Node failed to start!', error)
+      }
+    })
+    ```
+
+2. If you pass a function as the final argument, it will be called when the node is started (Note: this method will **not** return a promise if you use a callback function).
+
+    ```js
+    const node = new IPFS({ start: false })
+
+    node.on('ready', () => {
+      console.log('Node is ready to use!')
+
+      node.start(error => {
+        if (error) {
+          return console.error('Node failed to start!', error)
+        }
+        console.log('Node started!')
+      })
+    })
+    ```
+
 3. You can listen for the [`start` event](#events).
 
-```js
-const node = new IPFS({ start: false })
+    ```js
+    const node = new IPFS({ start: false })
 
-node.on('ready', () => {
-  console.log('Node is ready to use!')
-
-  // Use a promise:
-  node.start()
-    .then(() => console.log('Node started!'))
-    .catch(error => console.error('Node failed to start!', error))
-
-  // OR use a callback:
-  node.start(error => {
-    if (error) {
-      console.error('Node failed to start!', error)
-      return
-    }
-    console.log('Node started!')
-  })
+    node.on('ready', () => {
+      console.log('Node is ready to use!')
+      node.start()
+    })
 
-  // OR use events:
-  node.on('error', error => console.error('Something went terribly wrong!', error))
-  node.on('start', () => console.log('Node started!'))
-  node.start()
-})
-```
+    node.on('error', error => {
+      console.error('Something went terribly wrong!', error)
+    })
+
+    node.on('start', () => console.log('Node started!'))
+    ```
 
 #### `node.stop([callback])`
 
@@ -392,33 +412,55 @@ Close and stop listening for connections with other IPFS nodes, then release acc
 This method is asynchronous. There are several ways to be notified when the node has completely stopped:
 
 1. If you call `node.stop()` with no arguments, it returns a promise.
-2. If you pass a function as the final argument, it will be called when the node is stopped. *(Note: this method will **not** return a promise if you use a callback function.)*
+
+    ```js
+    const node = new IPFS()
+
+    node.on('ready', async () => {
+      console.log('Node is ready to use!')
+
+      try {
+        await node.stop()
+        console.log('Node stopped!')
+      } catch (error) {
+        console.error('Node failed to stop cleanly!', error)
+      }
+    })
+    ```
+
+2. If you pass a function as the final argument, it will be called when the node is stopped (Note: this method will **not** return a promise if you use a callback function).
+
+    ```js
+    const node = new IPFS()
+
+    node.on('ready', () => {
+      console.log('Node is ready to use!')
+
+      node.stop(error => {
+        if (error) {
+          return console.error('Node failed to stop cleanly!', error)
+        }
+        console.log('Node stopped!')
+      })
+    })
+    ```
+
 3. You can listen for the [`stop` event](#events).
 
-```js
-const node = new IPFS()
-node.on('ready', () => {
-  console.log('Node is ready to use!')
-
-  // Stop with a promise:
-  node.stop()
-    .then(() => console.log('Node stopped!'))
-    .catch(error => console.error('Node failed to stop cleanly!', error))
-
-  // OR use a callback:
-  node.stop(error => {
-    if (error) {
-      console.error('Node failed to stop cleanly!', error)
-      return
-    }
-    console.log('Node stopped!')
-  })
+    ```js
+    const node = new IPFS()
 
-  // OR use events:
-  node.on('error', error => console.error('Something went terribly wrong!', error))
-  node.stop()
-})
-```
+    node.on('ready', () => {
+      console.log('Node is ready to use!')
+      node.stop()
+    })
+
+    node.on('error', error => {
+      console.error('Something went terribly wrong!', error)
+    })
+
+    node.on('stop', () => console.log('Node stopped!'))
+    ```
 
 #### Core API