[Devcontainers frontend plugin] Make the component hidden if no annotation is present

[ipe4647]

If the annotation is not present, make the DevcontainersProvider component hidden.

This should be working in packages/app/src/components/catalog/EntityPage.tsx:

    <EntitySwitch>
    <EntitySwitch.Case if={isDevContainersAvailable}>
    <Grid item md={6} xs={12}>
      <DevcontainersProvider config={devcontainersConfig}>
        <ExampleDevcontainersComponent/>
      </DevcontainersProvider>
    </Grid>
    </EntitySwitch.Case>
    </EntitySwitch>

The isDevContainersAvailavble function should check if the correct annotations are in place like (pseudocode):

export const isDevContainersAvailable = (entity: Entity) =>
  Boolean(entity.metadata.annotations?.[DEVCONTAINERS_ANNOTATION]);

This way the item can be hidden and the page can be cleaner.