Improve visibility of Setup/Installation topics

[jcalcaben]

This issue is a:

[ ] Bug
[ ] New Topic Request
[X] Topic Clarification Request
[ ] New Feature Request
[ ] Other

Description:

Currently, it is not obvious where to go to set up the pwa-buildpack or venia-theme projects.

Steps to Reproduce

1. Go to front page - no mention of installation or setup
2. Go to pwa-buildpack section from front page - no mention of installation or setup on landing page content
3. Go to venia-theme section from front page - no mention of installation or setup on landing page content'
4. Go to project repos and see old installation instructions

Expected Result:

New users/contributors looking to get started with or install the project are able to navigate to the correct topic in as few clicks as possible and in more obvious ways.

Possible Solutions:

• Replace one of the box contents on the front page with a Getting started section with links to setup/installation for venia and buildpack
• Add a link to the overview pages of pwa-buildpack and venia-theme that go to each section's setup/installation topic.
• Replace installation instructions on the project repos and link to appropriate devdocs pages

Additional Information:

This issue is based on feedback from @paliarush