mark tailwindcss as a peer dependency

This plugin uses tailwindcss internally, but marks it only as a dev dependency rather than a peer dependency, causing errors/undefined behavior in monorepos and Yarn PNP. Correctly adding tailwind as a peer dependency allows for correct resolution to occur while still referencing the *user's* tailwind and not an internal version.

Other official plugins have already corrected this: see tailwindlabs/tailwindcss-forms@8a8671b

This pull request is identical to tailwindlabs/tailwindcss-line-clamp#6. Both other official plugins (forms, typography) already correctly use peer dependencies.

package.json

@@ -15,6 +15,9 @@
   },
   "scripts": {
     "prepublishOnly": "node scripts/build.js"
+  },
+   "peerDependencies": {
+    "tailwindcss": "^2.0.0"
   },
   "devDependencies": {
     "autoprefixer": "10",