make separate function for gemgetting

tidy Makefile

add manpage

incomplete mimetype detection

a possible header response is
200 text/gemini; charset=utf-8
So, the mimetype should be found by scanning up to ';' or EOF.

add Makefile

s/^I/    /g

rename to gm

add log() and die() for more concise error messages

pass a pointer to string to Prettify

basic response code handling

add go.mod

add LICENSE

initial