How to use forked rete repo as npm dependency in Angular 8

[WieFel]

I have forked this repository and want to use my custom version as a dependency in Angular 8.

However, using the following dependencies in package.json doesn't work:

...
    "rete": "github:wiefel/rete",
    "rete-angular-render-plugin": "^0.2.0-rc.1",
    "rete-area-plugin": "^0.2.1",
    "rete-connection-plugin": "^0.9.0",
    "rete-context-menu-plugin": "^0.5.2",
    "rete-minimap-plugin": "^0.3.1",
...

The rete folder inside node_modules doesn't contain any code folders:

.
├── CONTRIBUTING.md
├── LICENSE
├── package.json
├── README.md
├── rete.config.js
├── sonar-project.properties
└── tsconfig.json

While the other dependencies' folders (e.g. "rete-angular-render-plugin") do contain code.

What am I doing wrong?

[WieFel]

Solved it by adding

"prepare": "npm run build"

at the end of "scripts": { ... } in package.json.