Add disclaimer banner to any public-facing documentation (docusaurus webpage)

[Sophietn]

Banner disclaimer wording:

[!important] Incubation Project This project is an incubation project being run inside the Green Software Foundation; as such, we *DON’T recommend using it in any critical use case. Incubation projects are experimental, offer no support guarantee, have minimal governance and process, and may be retired at any moment. This project may one day graduate, in which case this disclaimer will be removed.

[danuw]

Example banner given by @Sophietn currently visible at https://if.greensoftware.foundation/

[Sophietn]

Here's the PR for adding it to the IF document website, in the IF-docs repo Green-Software-Foundation/if-docs#11

[danuw]

trying to use https://docusaurus.io/docs/api/themes/configuration#announcement-bar - adding link for reference

as well as this https://docusaurus.io/docs/styling-layout#global-styles for options that are not yet available and need overriding

[danuw]

@Sophietn can you double check - should look something like below.

Please note, using out of the box announcement bar, so disclaimer can be closed and should only reappear on the same browser when we increment the announcement id.

[danuw]

I have since bolded the message

[Sophietn]

LGTM thank you