feat(styles): one stylesheet source for react and svelte (#3350)

* feat(styles): create stylesheets for react and svelte based on one source

* refactor(styling): cleanup

* refactor(postcss): share a config

* refactor(postcss): replace env hack with env file

package.json

@@ -22,17 +22,11 @@
     "@changesets/cli": "^2.25.0",
     "@typescript-eslint/eslint-plugin": "latest",
     "@typescript-eslint/parser": "latest",
-    "autoprefixer": "^10.4.8",
     "concurrently": "^7.6.0",
     "eslint": "^8.22.0",
     "eslint-config-prettier": "^8.5.0",
     "eslint-plugin-prettier": "^4.2.1",
     "eslint-plugin-react": "latest",
-    "postcss": "^8.4.21",
-    "postcss-cli": "^10.1.0",
-    "postcss-combine-duplicated-selectors": "^10.0.3",
-    "postcss-import": "^15.1.0",
-    "postcss-nested": "^6.0.0",
     "prettier": "^2.7.1",
     "react": "^18.2.0",
     "react-dom": "^18.2.0",