Add a new "English (US, 102nd key is backslash)" variant

Most keyboards sold in the Netherlands use the standard US keyboard layout (with euro on 5), but they use the ISO physical-keyboard-layout which has an extra 102nd key between the left Shift and the Z key. This extra key is marked as a second backslash/bar key.

us(euro) does not contain a specific binding for key <LSGT>, so it inherits the standard less/greater binding from the pc105 symbols, resulting in the key sending the wrong symbols.

There have been a few reports on forums about this issue over the years:

• https://www.reddit.com/r/techsupport/comments/lgrxc/in_ubuntu_my_backslashpipe_key_types_less/
• http://forum.notebookreview.com/threads/g51-linux-backslash-pipe-key-remapping.405784/
• https://askubuntu.com/questions/259334/need-to-change-a-key-from-greater-than-less-than-to-backslash-pipe
• https://askubuntu.com/questions/1103370/ubuntu-18-04-backslash-key-incorrectly-mapped-in-ansi-keyboard-english-us

I assume that there are actually keyboards out there which use a "English (US)" layout where the 102nd key is marked as less/greater, so just changing the "English (US, euro on 5)" variant would break other people's setups.

Add a new "English (US, 102nd key is backslash)" variant which users of these keyboards can use to get the correct bindings.