Signature Pad

Build a custom element based on the third-party NPM module signature_pad.

The app uses the signature_pad node module to create a signature pad. In package.json, the signature_pad module is listed as a dependency, while signature_pad.js and signature_pad.py define the new UI element which can be used in main.py.

Furthermore, rollup is used to bundle and minify the signature_pad module and places the result in the dist directory. The rollup configuration is in rollup.config.mjs. The entry point is defined in src/index.mjs, basically just re-exporting the signature_pad module.

First, install the third-party node modules (assuming you have NPM installed):
bash
```
npm install
```
This will create a node_modules directory containing the signature_pad module.
Build the signature_pad module:
bash
```
npm run build
```
This will create a dist directory containing the signature_pad module.
Now you can run the app as usual:
bash
```
python3 main.py
```