styled-react: Export BaseStyles (#6968)

Co-authored-by: Marie Lucca <40550942+francinelucca@users.noreply.github.com>

Author: siddharthkp

.changeset/tricky-plums-smoke.md

@@ -0,0 +1,5 @@
+---
+"@primer/styled-react": patch
+---
+
+Export BaseStyles

packages/styled-react/src/__tests__/__snapshots__/exports.test.ts.snap

@@ -6,6 +6,7 @@ exports[`@primer/styled-react exports 1`] = `
  "ActionMenu",
  "Autocomplete",
  "Avatar",
+ "BaseStyles",
  "Box",
  "Breadcrumb",
  "Breadcrumbs",

packages/styled-react/src/index.tsx

@@ -16,6 +16,7 @@ export {theme} from '@primer/react'
 export {themeGet} from '@primer/react'
 export {useColorSchemeVar} from '@primer/react'
 export {useTheme} from '@primer/react'
+export {BaseStyles} from '@primer/react'
 
 export {
  ActionList,