Landing Page

[H-Richard]

We want guests and users alike to see a landing page upon visiting.
This page is to be served on / and displays current active job posts.

This issue is blocked by #15

We want it to look something like this
except instead of the division, display when the post was created and the person that posted it.

Out of Scope: Upon clicking the title, the user should be taken to /{id} where they can view the post in detail.
Out of Scope: Upon clicking the apply, if logged in, a modal is shown where the user can apply, if user is not logged in, take them to /login

Acceptance Tests:

• Posts are saved to the store
• Posts are retrieved via selectors
• Posts are accessed in / via mapStateToProps
• Separate postCards component in components/common/
• Page looks good with light/dark theme