Updated quicklinks on index.html and narrative.html

[yantosca]

Name and Institution (Required)

Name: Bob Yantosca Institution: Harvard + GCST

Confirm you have reviewed the following documentation

• [x] Contributing guidelines

Describe the update

1. Added a "Download and run GEOS-Chem" link to index.html
2. Consolidated all quicklinks into a single row underneath the "current release" box.
3. Centered the page title on "narrative.html"
4. Added page breaks to prevent quicklinks on the "narrative.html" from wrapping to the next line

Expected changes

Aesthetic updates only

Related Github Issue(s)

N/A