feat: Add grid and responsive template sizing, resolve #33

[chethtrayen]

PR Checklist

• [x] Addresses an existing open issue: fixes #033
• [x] That issue was marked as status: accepting prs
• [x] Steps in CONTRIBUTING.md were taken

Overview

Update page-grid display from flex to grid. Add responsive column and row scaling by using minmax.

[tjwds]

LGTM, thanks!