clarify intro paragraph and getting started section - specific initial suggestions

[ownsourcing]

Linking to the issue filed by @JamesHurburgh in the grunt-docs issue queue. It appears to refer to this repo.

Getting started should explain what Grunt actually does https://github.com/gruntjs/grunt-docs/issues/196 JamesHurburgh opened this issue on Jan 14 · 2 comments

We're happy to expand on our recommended fixes if there is a desire among maintainers. Rewrite of the opening paragraph should of course be reflected in a rewrite of other content on the homepage.