DOC: Installation page additions

[siwood]

Using installation instructions from the https://cucumber.io/docs#installation pages to add Javascript and Ruby instructions. Adding some structure to the installation part of the SUMMARY.md menu.

[tsundberg]

I looked at this pull request and think it can be merged.

It may be a bit large as it covers both installation and Three Amigos, but it is not a biggi in my book.

[brasmusson]

@tsundberg The Three Amigos is already merged (https://docs.cucumber.io/docs/techniques.html#three-amigos), but habit of @siwood to merge from cucmber:master to the PR branch (instead of rebaseing), will make the list of commits in the PR longer than it should be.

[tsundberg]

@brasmusson what is your proposal? Merge or not merge?

[siwood]

@brasmusson I'm new to git. I will try rebasing next time to avoid the annoying extra commits. Thanks for pointing that out!

[siwood]

Ok, I think it's cleaned up.

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.