vscode: let cSpell work on commit messages, too

By default, the cSpell extension ignores all files under .git/. That includes, unfortunately, COMMIT_EDITMSG, i.e. commit messages. However, spell checking is *quite* useful when writing commit messages... And since the user hardly ever opens any file inside .git (apart from commit messages, the config, and sometimes interactive rebase's todo lists), there is really not much harm in *not* ignoring .git/. The default also ignores `node_modules/`, but that does not apply to Git, so let's skip ignoring that, too. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>