Add support for multiple -m flags in create and comment

[0xheartcode]

git commit supports multiple -m flags to build multi-paragraph messages. git issue create and git issue comment now match this behavior: each additional -m appends a new paragraph separated by a blank line.

git issue create 'Bug title' -m 'Context paragraph' -m 'Steps to reproduce'
git issue comment <id> -m 'Investigation notes' -m 'Proposed fix'

Single -m usage is unchanged. Changes are confined to the argument parsing loop in each script. Two tests added to t/test-issue.sh. Full suite: 284 passed, 0 failed.

Closes #138

[0xheartcode]

force pushed, updated docs to 284 tests.

[remenoscodes]

Clean implementation — mirrors git commit multi--m behavior correctly. The printf '%s\n\n%s' approach handles paragraph joining well, and single -m usage is unaffected.

Tests pass locally (all 204). CI didn't trigger — likely needs first-time contributor workflow approval in the Actions tab.

Minor note: commit message should use conventional commits format (feat: add support for multiple -m flags) when squash-merging.

LGTM ✓

[remenoscodes]

Implementation looks great — approved on the code side (tests pass, clean approach).

One change needed before merge: the commit message should follow Conventional Commits format, which this project requires for automated changelog generation:

feat: add support for multiple -m flags in create and comment

Currently it's:

Add support for multiple -m flags in create and comment

Just needs the feat: prefix. You can fix it with:

git commit --amend -m "feat: add support for multiple -m flags in create and comment"
git push --force-with-lease

Once that's updated, this is ready to merge. Thanks!