Update NVDA icon
See PR #7446
Include the source `svg` so that future modifications can be made more
easily.
The previous dark grey shaded icon has been in use for nearly 10 years.
It was first created for Windows XP, which had a light grey system tray
which showed up the dark grey logo very well. Recent versions of
Windows have moved towards a darker system tray. There is very little
contrast with the existing NVDA icon. The updated icon features a
similar logo in flat white, on a solid purple background. This ensures it
will be visible on any colour background, and uses the purple from the
NV Access logo.
The NVDA logo is a stylised blend of the letters NVDA. It has a vertical
line on the left with a little hook at the bottom. Then from the top, a
straight diagonal line comes down to the right. Next, a line curves in a
semi-circle out to the right then back up to the top, and finally there
is a little hook down to finish. The vertical and diagonal lines make
the first part of the letter N and also the letter A (without the cross
bar). The diagonal and curved lines form a V, and the curve is the right
part of the D.
