feat: Add Stories for o-banner demos

[notlee]

Destroy Method

Adds a destroy method to o-banner. This is used in the o-banner
Story to clean up the close button when re-rendered, which o-banner
dynamically creates on init. This is required to support the
suppressCloseButton Story control.

Hidden Controls

It appears banner headings (headingLong/headingShort) should only
be used with the small/compact layout variants. Not with the default
banner style which is full bleed. However it is possible to use
Story controls to create that view.

ok: default layout story

bad: theme story, with layout changed to the default layout via a control
(the default layout shouldn't be used with a heading)

@storybook/addon-knobs (deprecated) allowed dynamic knobs,
so we could hide the heading controls if the default layout
was selected. That's not possible with @storybook/addon-controls:
storybookjs/storybook#11984

I think that's probably a good thing. Support for
dynamic controls was worked on but not merge. It's
a poor experience when controls shift around.
storybookjs/storybook#13890

For now this commit hides the layout control on layout
demos, and hides the heading controls from the default
layout demo, to avoid showing the discouraged
heading + layout combination. However it is still
possible to select the base layout with heading on the
theme specific demos, so that the small/compact layout
can also be selected which is allowed.

This could be resolved by exporting 2 templates, one
for each kind of banner / usecase. This could make
components easier to reason with and maintain. For
now this commit sticks to one banner template as
coming up with a name without history / useage
guidelines is difficult, and we don't know that
users aren't already using headings with the base
layout - though we never intended it as far as I
can tell.

No Custom Theme Demo

The custom theme demo has not been migrated to a Story
yet.
https://registry.origami.ft.com/components/[email protected]#demo-custom-theme

I'm not sure there is value, and maybe harm, in showing
made up customised styles alongside those with brand/design
approval. Plus it's not clear how to re-create the style
without understanding Sass and inspecting demo code.
We probably want to have stories for customised components
at a later date, with improved guidelines around them
and demo Sass/JS pane. See related issue:
#370

No Custom Call To Action Demo

https://registry.origami.ft.com/components/[email protected]#demo-custom-call-to-action-layout

The description of the demo starts "Although not recommended for
design consistency..." Let's not recomend it with a demo.

[JakeChampion]

I've reviewed the changes and left a suggestion and some questions

I deployed this to a review app but it looks to not work due to lots of responses returning 404s -- https://origami-webs-stories-o--wn51ap.herokuapp.com/storybook/

[notlee]

I deployed this to a review app but it looks to not work due to lots of responses returning 404s
🤔

...I deleted it, sorry