feat: provide descriptions

[danyill]

Closes #6

[danyill]

@JakobVogelsang I'm getting a lot of this in my unit tests:

🚧 Browser logs:
      Multiple versions of Lit loaded. Loading multiple versions is not recommended. See https://lit.dev/msg/multiple-versions for more information.
      TypeError: Illegal constructor
        at SampledValueControlElementEditor.attachShadow (node_modules/@open-wc/scoped-elements/html-element.js:74:25)
        at SampledValueControlElementEditor.createRenderRoot (node_modules/@open-wc/scoped-elements/lit-element.js:28:31)
        at SampledValueControlElementEditor.connectedCallback (node_modules/lit-element/node_modules/@lit/reactive-element/src/reactive-element.ts:1108:11)
        at SampledValueControlElementEditor.connectedCallback (node_modules/lit-element/src/lit-element.ts:187:10)
        at ChildPart._insert (node_modules/lit-html/src/lit-html.ts:1496:52)
        at ChildPart._commitNode (node_modules/lit-html/src/lit-html.ts:1540:35)
        at ChildPart._commitTemplateResult (node_modules/lit-html/src/lit-html.ts:1655:11)
        at ChildPart._$setValue (node_modules/lit-html/src/lit-html.ts:1469:11)
        at render (node_modules/lit-html/src/lit-html.ts:2269:7)
        at litFixtureSync (node_modules/@open-wc/testing-helpers/src/litFixture.js:32:3)

 ❌ Error: Uncaught TypeError: Illegal constructor (http://localhost:8000/node_modules/@open-wc/scoped-elements/html-element.js:74) 
      at ChildPart._insert (node_modules/lit-html/src/lit-html.ts:1496:52)
      at ChildPart._commitNode (node_modules/lit-html/src/lit-html.ts:1540:35)
      at ChildPart._commitTemplateResult (node_modules/lit-html/src/lit-html.ts:1655:11)
      at ChildPart._$setValue (node_modules/lit-html/src/lit-html.ts:1469:11)
      at render (node_modules/lit-html/src/lit-html.ts:2269:7)
      at litFixtureSync (node_modules/@open-wc/testing-helpers/src/litFixture.js:32:3)
      at litFixture (node_modules/@open-wc/testing-helpers/src/litFixture.js:63:14)
      at fixture (node_modules/@open-wc/testing-helpers/src/fixture-no-side-effect.js:62:12)
      at n.<anonymous> (editors/sampledvalue/sampled-value-control-element-editor.spec.ts:36:19)

I'd be very grateful if you could provide a small clue

[danyill]

Ah, no forget it I discovered the cause 😉

[danyill]

@JakobVogelsang I would be most grateful for a review and happy to make improvements.

The unit tests are running and passing except for some reason that escapes me they do not terminate - perhaps a missing brace somewhere.

[danyill]

The cause of the unit tests not passing are the following tests in the dataset-element-editor.spec.ts file:

 it('allows to move FCDA child one step up', async () => {
 it('allows to move FCDA child one step down', async () => {

I'm not sure why they are not working