Update Calisphere static page copy: reference web accessibility considerations with materials in the site

[aturner]

Working notes: https://docs.google.com/document/d/1vSqFxK3DffICIzV51V1Dg-Q8f-I2_o03hZH5KRoBLp8/edit?tab=t.i3yd03calnot

• Homepage: https://github.com/ucldc/public_interface/blob/main/calisphere/templates/calisphere/home.html
• About: https://github.com/ucldc/public_interface/blob/main/calisphere/templates/calisphere/about.html