Use customElements.define instead of document.registerElement

[ottok]

I am using this package in Pulsar and noticed that deprecations cop is nagging about:

Use customElements.define instead of document.registerElement see https://javascript.info/custom-elements

HTMLDocument.registerElement - file:///opt/Pulsar/resources/app.asar/static/index.js:100:12
Object.<anonymous> - [/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:75:29](https://github.com/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:75:29)
Object.<anonymous> - [/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:80:4](https://github.com/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:80:4)
Object.<anonymous> - [/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:84:3](https://github.com/home/otto/.pulsar/packages/nim/lib/nim-status-bar-view.coffee:84:3)
Module._compile - [/opt/Pulsar/resources/app.asar/src/native-compile-cache.js:120:30](https://github.com/opt/Pulsar/resources/app.asar/src/native-compile-cache.js:120:30)
Object..coffee - [/opt/Pulsar/resources/app.asar/src/compile-cache.js:252:23](https://github.com/opt/Pulsar/resources/app.asar/src/compile-cache.js:252:23)

Not a priority but you might want to address this at some point.

Thanks for a great plugin that helps me learn Nim faster! 🙏