issue-body from file

[AurimasNav]

Please consider adding issue-body from file feature, to workaround annoying new-lines not being preserved if we try to use multi-line output from another step from GITHUB_OUTPUTS.

Use case: tofu plan output is unreadable if saved and used from GITHUB_OUTPUTS, because new lines are not preserved.

[AurimasNav]

Managed to make it work with multiline values from outputs, however providing issue-body from file would be still a nice qol feature.