Add grow and shrink aliases (#5733)

This adds `grow-*` and `shrink-*` utilities as aliases for `flex-grow-*` and `flex-shrink-*` since those names are unnecessarily verbose. We will stop documenting the long form ones and consider them deprecated.

```diff
- <div class="flex-grow-0 flex-shrink">
+ <div class="grow-0 shrink">
```

tests/basic-usage.test.css

@@ -281,12 +281,24 @@
 .flex-shrink-0 {
   flex-shrink: 0;
 }
+.shrink {
+  flex-shrink: 1;
+}
+.shrink-0 {
+  flex-shrink: 0;
+}
 .flex-grow {
   flex-grow: 1;
 }
 .flex-grow-0 {
   flex-grow: 0;
 }
+.grow {
+  flex-grow: 1;
+}
+.grow-0 {
+  flex-grow: 0;
+}
 .basis-auto {
   flex-basis: auto;
 }