Resolve author and committer names through .mailmap

[ChrisJr404]

Closes #102.

serie builds its git log format string with the lowercase identity placeholders (%an, %ae, ...), so it always shows the raw name and email recorded in each commit. This switches to the uppercase variants (%aN, %aE, %cN, %cE) when a new core.option.mailmap option is enabled, which makes git resolve identities through the repository's .mailmap file, the same way git log and git shortlog do. Repositories without a .mailmap are unaffected, since the two placeholder forms produce identical output there.

I defaulted the option to true so it works out of the box like git's own tooling, but it's a plain boolean, so anyone who prefers the raw values can set mailmap = false. Happy to make it opt-in instead if you would rather keep the current default.

Added integration tests for the enabled, disabled, and no-.mailmap cases, and documented the option in the config reference and JSON schema.

[lusingander]

Thanks for working on this! Could you please make the following changes?

• Please add a new [core.git] section and move mailmap option under it.
• I’d like the default value to be false.
  • Enabling it by default would probably be fine and unlikely to cause problems, but for now I’d prefer to preserve the existing behavior.

[ChrisJr404]

Moved mailmap under a new [core.git] section and defaulted it to false to keep the existing behavior, as you suggested. Thanks!

[lusingander]

Thank you!