Add isolation:isolate to ButtonGroup container (#2910)

* Add `isolation:isolate` to `ButtonGroup` container

* Create .changeset/fair-lobsters-sin.md

* Update snapshots

Author: iansan5653

.changeset/fair-lobsters-sin.md

@@ -0,0 +1,5 @@
+---
+"@primer/react": patch
+---
+
+Add `isolation:isolate` to `ButtonGroup` container

src/ButtonGroup.tsx

@@ -6,6 +6,7 @@ import {ComponentProps} from './utils/types'
 const ButtonGroup = styled.div`
   display: inline-flex;
   vertical-align: middle;
+  isolation: isolate;
 
   && > * {
     position: relative;

src/__tests__/deprecated/__snapshots__/Button.test.tsx.snap

@@ -301,6 +301,7 @@ exports[`ButtonGroup renders consistently 1`] = `
   display: -ms-inline-flexbox;
   display: inline-flex;
   vertical-align: middle;
+  isolation: isolate;
 }
 
 .c0.c0 > * {