Add an issue template with prompting questions for update to landscape

[vielmetti]

Make it easier for people suggesting updates to the landscape by including an issue template that prompts them to answer questions suitable for incorporating changes in.

Follow https://help.github.com/articles/about-issue-and-pull-request-templates/

[vielmetti]

Suggestion:

I think we’d want people to provide things like (a) name of entry, (b) usage references that support change request

[vielmetti]

Adapt questions for landscape