Add experimental high contrast mode (#1845)

Add an experimental high contrast color theme to SCM-Manager. The high contrast mode uses a dark background and color with a high contrast for a better accessibility.
The change adds the theme to ui-styles and theme switcher to the storybook of ui-components.

scm-ui/ui-components/src/repos/Diff.stories.tsx

@@ -85,7 +85,7 @@ const fileControlFactory: (changeset: Changeset) => FileControlFactory = (change
   return links.map(({ url, label }) => <JumpToFileButton tooltip={label} link={url} />);
 };
 
-storiesOf("Diff", module)
+storiesOf("Repositories/Diff", module)
   .addDecorator(RoutingDecorator)
   .addDecorator((storyFn) => <Container>{storyFn()}</Container>)
   .add("Default", () => <Diff diff={diffFiles} />)

scm-ui/ui-components/src/repos/RepositoryEntry.stories.tsx

@@ -98,7 +98,7 @@ const archivedExportingRepository = {
     "Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.",
 };
 
-storiesOf("RepositoryEntry", module)
+storiesOf("Repositories/RepositoryEntry", module)
   .addDecorator((story) => <MemoryRouter initialEntries={["/"]}>{story()}</MemoryRouter>)
   .addDecorator((storyFn) => <Container>{storyFn()}</Container>)
   .add("Default", () => {

scm-ui/ui-components/src/repos/annotate/Annotate.stories.tsx

@@ -164,7 +164,7 @@ const Robohash: FC = ({ children }) => {
   return <BinderContext.Provider value={binder}>{children}</BinderContext.Provider>;
 };
 
-storiesOf("Annotate", module)
+storiesOf("Repositories/Annotate", module)
   .addDecorator(storyFn => <MemoryRouter initialEntries={["/"]}>{storyFn()}</MemoryRouter>)
   .addDecorator(storyFn => <Wrapper className="box">{storyFn()}</Wrapper>)
   .add("Default", () => (

scm-ui/ui-components/src/repos/changesets/Changesets.stories.tsx

@@ -71,7 +71,7 @@ function copy<T>(input: T): T {
   return JSON.parse(JSON.stringify(input));
 }
 
-storiesOf("Changesets", module)
+storiesOf("Repositories/Changesets", module)
   .addDecorator(story => <MemoryRouter initialEntries={["/"]}>{story()}</MemoryRouter>)
   .addDecorator(storyFn => <Wrapper className="box box-link-shadow">{storyFn()}</Wrapper>)
   .add("Default", () => <ChangesetRow repository={repository} changeset={three}/>)