Use double quotes in examples for CMD.exe support

See https://github.com/FiloSottile/mkcert/issues/60#issuecomment-415352403

README.md

@@ -8,7 +8,7 @@ Created a new local CA at "/Users/filippo/Library/Application Support/mkcert"
 The local CA is now installed in the system trust store! ⚡️
 The local CA is now installed in the Firefox trust store (requires restart)! 🦊
 
-$ mkcert example.com '*.example.org' myapp.dev localhost 127.0.0.1 ::1
+$ mkcert example.com "*.example.org" myapp.dev localhost 127.0.0.1 ::1
 Using the local CA at "/Users/filippo/Library/Application Support/mkcert" ✨
 
 Created a new certificate valid for the following names 📜

main.go

@@ -31,7 +31,7 @@ const usage = `Usage of mkcert:
 	$ mkcert example.com myapp.dev localhost 127.0.0.1 ::1
 	Generate "example.com+4.pem" and "example.com+4-key.pem".
 
-	$ mkcert '*.example.com'
+	$ mkcert "*.example.com"
 	Generate "_wildcard.example.com.pem" and "_wildcard.example.com-key.pem".
 
 	$ mkcert -pkcs12 example.com