Broken build

Following the instructions, the project compiles but emits a warning about unused ThinBackend
```
➜ myproject git:(master) ✗ npm run rescript:build

> rescript-project-template@0.0.1 rescript:build
> rescript

Dependency on @rescript/react
rescript: [38/38] src/legacy/ReactDOMRe.cmj
rescript: [49/49] install.stamp
Dependency on rescript-ihp-backend
rescript: [3/3] ThinBackend.cmj
rescript: [5/5] install.stamp
Dependency Finished
rescript: [5/6] src/App.cmj

Warning number 33
/home/late/projects/ocaml/web/myproject/src/App.res:1:1-16

1 │ open ThinBackend
2 │
3 │ @react.component

unused open ThinBackend.

rescript: [6/6] src/Main.cmj
```

When trying to launch the development server, ThinBackend resolution fails
```
➜ myproject git:(master) ✗ npm run dev

> rescript-project-template@0.0.1 dev
> node server.js

> src/Main.bs.js:6:28: error: Could not resolve "ihp-backend" (mark it as external to exclude it from the bundle)
6 │ import * as IhpBackend from "ihp-backend";
╵ ~~~~~~~~~~~~~

> src/App.bs.js:4:25: error: Could not resolve "ihp-backend/react" (mark it as external to exclude it from the bundle)
4 │ import * as React$1 from "ihp-backend/react";
╵ ~~~~~~~~~~~~~~~~~~~

Development server running on http://localhost:3000
```
I guess `ihp-backend` is the old name of the dependency...