build: wip re-add lerna.json

Lerna supports pnpm [1], and auto (for automatic publishing and github
label integration) requires lerna. Luckily lerna stays almost entirely
hands-off when pnpm is involved :)

[1] https://lerna.js.org/docs/recipes/using-pnpm-with-lerna

lerna.json

@@ -0,0 +1,8 @@
+{
+  "npmClient": "pnpm",
+  "useWorkspaces": true,
+  "version": "independent",
+  "$schema": "node_modules/lerna/schemas/lerna-schema.json",
+  "useNx": false,
+  "registry": "https://registry.npmjs.org"
+}