fix: Add :where selector to classes that land on nodes that have a sx prop (#4870)

* Add :where selector to classes that land on nodes that have a sx prop

* Create blue-stingrays-decide.md

Author: jonrohan

.changeset/blue-stingrays-decide.md

@@ -0,0 +1,5 @@
+---
+"@primer/react": patch
+---
+
+Add `:where()` selector to classes that land on nodes that have a `sx` prop.

packages/react/src/Heading/Heading.module.css

@@ -1,4 +1,4 @@
-.Heading {
+:where(.Heading) {
   margin: 0;
   font-size: var(--text-title-size-large);
   font-weight: var(--base-text-weight-semibold);

packages/react/src/Link/Link.module.css

@@ -1,4 +1,4 @@
-.Link {
+:where(.Link) {
   color: var(--fgColor-accent);
   text-decoration: none;