chore: Make mdx-deck a peerDependency

Author: Andrey Okonetchnikov

package.json

@@ -23,19 +23,22 @@
     "format": "prettier --loglevel warn --write \"**/*.{js,jsx,md,mdx}\""
   },
   "dependencies": {
-    "mdx-deck": "^4.1.1",
     "prop-types": "^15.7.2",
     "react-live": "2.2.2",
     "react-syntax-highlighter": "^12.2.1",
     "react-tweet-embed": "1.2.2",
     "theme-ui": "0.3.1"
   },
   "devDependencies": {
+    "mdx-deck": "^4.1.1",
     "husky": "^4.2.3",
     "lint-staged": "^10.1.2",
     "patch-package": "6.2.2",
     "prettier": "^2.0.4"
   },
+  "peerDependencies": {
+    "mdx-deck": "^4.1.1"
+  },
   "husky": {
     "hooks": {
       "pre-commit": "lint-staged"