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

packages/svelte/package.json

@@ -12,10 +12,12 @@
     "xyflow"
   ],
   "scripts": {
-    "dev": "vite dev",
+    "dev": "concurrently \"vite dev\" pnpm:css-watch",
     "build": "svelte-kit sync && svelte-package -o dist",
     "check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
     "check:watch": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json --watch",
+    "css": "postcss src/styles/{base,style}.css --config ./../../tooling/postcss-config --dir dist",
+    "css-watch": "pnpm css --watch",
     "lint": "prettier --plugin-search-dir . --check . && eslint .",
     "format": "prettier --plugin-search-dir . --write .",
     "typecheck": "pnpm check"
@@ -43,9 +45,18 @@
     "@sveltejs/package": "^2.2.1",
     "@typescript-eslint/eslint-plugin": "^5.60.0",
     "@typescript-eslint/parser": "^5.60.0",
+    "autoprefixer": "^10.4.15",
+    "cssnano": "^6.0.1",
+    "dotenv": "^16.3.1",
     "eslint": "^8.43.0",
     "eslint-config-prettier": "^8.8.0",
     "eslint-plugin-svelte": "^2.31.1",
+    "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",
+    "postcss-rename": "^0.6.1",
     "prettier": "^2.8.8",
     "prettier-plugin-svelte": "^2.10.1",
     "svelte": "^4.2.0",