Updates Warning icon, Adds Pin icon (#1925)

* test

* runs lint

Author: bruugey

.changeset/odd-fans-watch.md

@@ -0,0 +1,5 @@
+---
+'@leafygreen-ui/icon': minor
+---
+
+Adds `Pin` icon and updates `Warning` icon to match Figma specs

packages/icon/README.md

@@ -91,6 +91,7 @@ import Pause from './Pause.svg';
 import Person from './Person.svg';
 import PersonGroup from './PersonGroup.svg';
 import PersonWithLock from './PersonWithLock.svg';
+import Pin from './Pin.svg';
 import Play from './Play.svg';
 import Plus from './Plus.svg';
 import PlusWithCircle from './PlusWithCircle.svg';
@@ -228,6 +229,7 @@ const _glyphs = {
   Person,
   PersonGroup,
   PersonWithLock,
+  Pin,
   Play,
   Plus,
   PlusWithCircle,