Release notes entry for new mobile-header-text-color

Adding a release notes entry for the addition of mobile-header-text-color
in colors.tt2.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Ben Shum <bshum@biblio.org>
lp1261791 Adjustment to background color for mobile search links

Adding an id for the div surrounding mobile search links so that the
background color matches the color of the rest of the header.

Signed-off-by: Kathy Lussier <klussier@masslnc.org>
Signed-off-by: Ben Shum <bshum@biblio.org>
Move new color note to release notes 2.7

Signed-off-by: Ben Shum <bshum@biblio.org>