[Backport 7.x] ESM support (#1236)

Co-authored-by: Tomas Della Vedova <delvedor@users.noreply.github.com>

index.mjs

@@ -0,0 +1,10 @@
+import mod from './index.js'
+
+export default mod
+export const Client = mod.Client
+export const Transport = mod.Transport
+export const ConnectionPool = mod.ConnectionPool
+export const Connection = mod.Connection
+export const Serializer = mod.Serializer
+export const events = mod.events
+export const errors = mod.errors