add something about how we expect to work infra updates

The wrangler project does some bundling for us, that we are not
ready to reproduce here. So for the time being, we will do this
manually

.gitignore

@@ -1,2 +1,3 @@
 zig-cache/
 zig-out/
+core

README.md

@@ -8,6 +8,10 @@ Until we're better
 2. Add `worker_name.txt` to `src/` with CloudFlare worker name
 3. `zig build run`
 
+Getting new index.js
+--------------------
+
+* Run a real wrangler deploy, then go into the console and copy/paste
 
 Steps we take:
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