Update README.ja.md

fix typo &nbdash; to &ndash;
maybe typo.

fix '**スペース**' to ' **スペース** '
(must surround space to emphasis word)

fix '(ハード)タブ' to 'ハードタブ'
(match the original English version. 'hard tabs' not use parentheses)

fix 'good' to '良い例'
still not translate to japanese