missing unicode double vertical line

[Jeff Fessler]

the current source code supports this: ∥
Unicode Character 'PARALLEL TO' (U+2225)
https://www.fileformat.info/info/unicode/char/2225/index.htm

but not this: ‖
Unicode Character 'DOUBLE VERTICAL LINE' (U+2016)
https://www.fileformat.info/info/unicode/char/2016/index.htm

I need the missing one because it is what you get with \Vert<tab> in julia REPL

I'll try to make a PR.

[Jeff Fessler]

In case it helps others, I just found a workaround for now in my latex source:
\DeclareUnicodeCharacter{8214}{$\|$}

[Mykel Kochenderfer]

Thanks for the PR!