feat: Save Outline Icon for QX Editor

[brandenTenbrink]

Closes https://github.com/influxdata/clockface/issues/833

Changes

Adds a Save Outline Icon to the icon set

Screenshots

Checklist

Check all that apply

• [x] Updated documentation to reflect changes
• [x] Added entry to top of Changelog with link to PR (not issue)
• [x] Tests pass
• [x] Peer reviewed and approved