fix(form): add missing accent colors for core

Mimicing frontera accent colors, because CMS button design¹ show those:
https://xd.adobe.com/view/b37b291a-7798-4814-90f3-7ac63c48a3e0-e628/screen/d7a72466-4ae8-43fd-9531-44e033245ddb/

Using "Color Button" style² cuz it has more contrast than CMS¹ designs.³

¹ The left two columns ("On Light", "On Dark") are for CMS.
² I.e. .c-button--primary
³ Designer says his CMS designs lack contrast, and he will redesign.

taccsite_cms/static/site_cms/css/src/_imports/settings/color.css

@@ -0,0 +1,13 @@
+@import url("@tacc/core-styles/source/_imports/settings/color.css");
+
+:root {
+  /* Accent Hues */
+  --global-color-accent--x-light: #F2DFBD; /* originally #e3d7fd */
+  --global-color-accent--light: #BDA374;   /* originally #a387ed */
+  --global-color-accent--normal: #877453;  /* originally #784fe8 */
+  --global-color-accent--dark: #64563E;    /* originally #6039cc */
+  --global-color-accent--x-dark: #403014;  /* originally #3d189b */
+
+  --global-color-accent--alt: #E0D8C9;     /* originally #d2cce7 */
+  --global-color-accent--weak: #9D702140;  /* originally #6039cc40 */
+}