fix: updated nodejs requirement (#209)

As conversation mantained in discord
[here](https://discordapp.com/channels/1247475892435816553/1273237594985201816/1341772674875134032),
`w3cli` tool will not work correctly when uploading multiple files and
subfolder with the command `w3 up *` when using node 18.x and 20.x.
Works fie on node 22.x and 23.x , so changing requirement here.

README.md

@@ -4,7 +4,7 @@
 
 ## Getting started
 
-Install the CLI from npm (**requires Node 18 or higher**):
+Install the CLI from npm (**requires Node 22 or higher**):
 
 ```console
 npm install -g @web3-storage/w3cli