The word “highbright” was spelled as “hightbright” in a few places.

This will fall back to Tramp's shell if the login shell cannot
be determined.

Lets the user specify a shell for all Tramp methods.

Lets the user specify 'login-shell as a SHELL in
`vterm-tramp-shells', which leads to vterm starting with the
remote location's login shell.

Set the truncation slot for 'buffer-display-table' to the ASCII code for
a space character (32) to make the vterm buffer display a space instead
of the default truncation character ($) when a line is truncated.

- When checking for vterm-mode, also support modes derived from vterm

When use [lf](https://github.com/gokcehan/lf) to list files, emacs-libvterm may
read partial multi-byte character, for example:

  $ echo -n '招聘' | hexdump -C
  00000000  e6 8b 9b e8 81 98

  ; get "招", control sequence and partial character
  (vterm--filter process "\xE6\x8B\x9B\e[14;111H\xE8")

  ; now full "聘"
  (vterm--filter process "\x81\x98")

This will send "\xE8" to libvterm which is not a full character.