1970 playground select, side nav and section container

[GCHQ-Developer-299]

Summary of the changes

Add Storybook playgrounds for Select, SideNav and Section Container
Small fix to Section Container for when you change 'aligned' prop to null after first render (as what happens in the storybook)

Related issue

#1970

[github-actions]

View your branch deployment here: https://mi6.github.io/ic-ui-kit/branches/1970-playground-select-and-side-nav/web-components
View your React branch deployment here: https://mi6.github.io/ic-ui-kit/branches/1970-playground-select-and-side-nav/react
View your NextJs branch deployment here: https://mi6.github.io/ic-ui-kit/branches/1970-playground-select-and-side-nav/nextjs

[github-actions]

Cypress visual tests failed.
View the image diff here: https://github.com/mi6/ic-ui-kit/tree/gh-pages/branches/1970-playground-select-and-side-nav/cypress-image-diff-screenshots
View the html report here: https://github.com/mi6/ic-ui-kit/tree/gh-pages/branches/1970-playground-select-and-side-nav/cypress-image-diff-html-report

[ad9242]

found a slight issue in the select playgrounds: if you set loading to true, then back to false, it doesn't clear & you can no longer see the options

[GCHQ-Developer-299]

found a slight issue in the select playgrounds: if you set loading to true, then back to false, it doesn't clear & you can no longer see the options

I've found the issue I think - the loadingHandler function doesn't consider leaving loading...

  @Watch("loading")
  loadingHandler(newValue: boolean): void {
    newValue && this.triggerLoading();
  }

Raised a ticket for this: #2003