An update for theme.nss

[AndresF2016]

With this change made on theme.nss, it will look more closely match the default Windows 11 context menu design:

• Adjusted border, prefix, separator and orientation.
• Repainted both border and shadows (It adjusts atomically, depending on whether it is in light or dark mode).
• Font set to “Segoe UI Variable Text”, the same font used for the W11 default context menu.
• In addition, accent colours have been added to the glyph icons (it works in both light and dark mode).

Example:

PD: This is a small change, but it is beneficial for consistency.

[MishaProductions]

Thanks for your contribution, however note that Rectify11 v4 will no longer use nilesoft shell.