Update gitignore
Update gitignore

Signed-off-by: James Tsai <b59016c495bf386e2ecb186afd6e7e948bfa6a2e@gmail.com>

jackycute/HackMD,jackycute/HackMD,hackmdio/hackmd,hackmdio/hackmd,hackmdio/hackmd,jackycute/HackMD