Upgrade to Node v18 / npm v8

Hi everyone,

When I try to `npm install` after fresh clone, I get the following error:

```console
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR!
npm ERR! While resolving: contentlayer-docs@0.1.0
npm ERR! Found: react@18.0.0
npm ERR! node_modules/react
npm ERR! react@"18.0.0" from the root project
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer react@"^16.8 || ^17.0" from @radix-ui/react-dropdown-menu@0.1.6
npm ERR! node_modules/@radix-ui/react-dropdown-menu
npm ERR! @radix-ui/react-dropdown-menu@"^0.1.6" from the root project
```

I'm using `node v18.1.0 (npm v8.8.0)`

Does anyone has the same problem?