Add [t]csh support

[vaygr]

I was trying to install hstr on OPNsense (which is FreeBSD-based) and wondering if it's a heavy lift to add [t]csh support to hstr.

The format of ~/.history is quite simple:

...
#+1654572409
vi /usr/local/etc/ssh/sshd_config
#+1654572632
ls -lha
#+1654572649
...

And I tried to link ~/.history to ~/.bash_history to test and it worked fine with this in ~/.cshrc:

alias hh hstr                    # hh to be alias for hstr
setenv HSTR_CONFIG hicolor       # get more colors
bindkey -s "^R" "^A hstr -- ^J"  # bind hstr to Ctrl-r

So it seems only #-prefixed lines need to be ignored.

#111 touched it briefly, but so far only zsh made it to the list of supported shells.