Create introduction index page

[smckeon-so]

Create a new index page with a short introduction paragraphs of what Aranya is and what it can be used for.

[smckeon-so]

Being done as part of #26
This will be it's own PR.

[smckeon-so]

Taken from meeting notes with Caitlin:

We want to update the index to sections and hierarchical. Initial thoughts for the high level sections:

• Aranya Overview
  • This will include overview and any user guides, etc.
• Getting Started
  • This is the walkthrough tutorial
• Example Code and Use Cases
  • We might not have these now, but will want to in the future
• Specs

Home Page:

Index Overview Blurb is good

For the overview page content:

We will want to update this to align with the subsections we align on above. This is exactly what I was thinking in regard to one sentence on what each item is.

Overall, I think this is the right level of content and we don’t need to add additional detail.

[smckeon-so]

We've pivoted slightly following a work session with Yael to the following.

• Overview (index page)
  • A couple paragraphs pulled from the larger overview doc (what is Aranya and what can i use it for)
    • Include also capabilities section from wiki page (https://git.spideroak-inc.com/spideroak-inc/aranya-docs/wiki/Our-Products%3A-Aranya#what-are-aranyas-key-capabilities) and/or the "capabilities" section in overview.md
  • Data flow diagram
  • Support section