Modal: Add default elevation (#681)

* feat(modal): add elevation token

Adds elevation token level 5 to the modal component.

* chore: add changeset

* feat(modal-elevation): remove border and move elevation to modal__content class

---------

Co-authored-by: Markell Torres <markell.torres@ithaka.org>

Author: brentswisher

.changeset/calm-weeks-own.md

@@ -0,0 +1,5 @@
+---
+'@ithaka/pharos': minor
+---
+
+Add elevation style to modal component

packages/pharos/src/components/modal/pharos-modal.scss

@@ -94,9 +94,9 @@
   overflow-y: scroll;
   background-color: var(--pharos-modal-color-background-content);
   background-clip: padding-box;
-  border: 1px solid var(--pharos-modal-color-border-content);
   border-radius: var(--pharos-radius-base-standard);
   outline: 0;
+  box-shadow: var(--pharos-elevation-level-5);
 }
 
 .modal__body {