docs: add no-nesting examples (#120)

Author: ChristianMurphy

docs/rules/no-nesting.md

@@ -1 +1,30 @@
 # Avoid nested `then()` or `catch()` statements (no-nesting)
+
+#### Valid
+
+```js
+myPromise
+  .then(doSomething)
+  .then(doSomethingElse)
+  .catch(errors)
+```
+
+#### Invalid
+
+```js
+myPromise.then(val => {
+  doSomething(val).then(doSomethingElse)
+})
+
+myPromise.then(val => {
+  doSomething(val).catch(errors)
+})
+
+myPromise.catch(err => {
+  doSomething(err).then(doSomethingElse)
+})
+
+myPromise.catch(err => {
+  doSomething(err).catch(errors)
+})
+```