Use Markdown link references

[arhohuttunen]

It would be nice to be able to use Markdown link references to keep the unrendered Markdown form of the changelog readable. This is recommended for example when following Keep a Changelog or Common Changelog formats.

For example:

## [1.0.1] - 2019-08-24

### Fixed

- Prevent segmentation fault upon `close()`

## [1.0.0] - 2019-08-23

_Initial release._

[1.0.1]: https://github.com/owner/name/releases/tag/v1.0.1
[1.0.0]: https://github.com/owner/name/releases/tag/v1.0.0

[miniscruff]

Hmm, there is currently no method of adding a changelog footer like there is for headers. Nor would the header even include the data you would need to build this. It is an interesting idea and actually brings up some confusing parts of the config as I was looking around. The key of header is used in many places in similar but slightly different ways. I'm going to take a little time to see if I can fix the inconsistencies and include the option to support this feature.

Can't say when though, but I do like the idea.

[miniscruff]

Small update to this, after some thought I definitely want to overhaul, in a backwards compatible way, the different file and format strings in the configuration. I will make one or more tickets to handle this migration. Namely I think including changelog header/footer file and format configuration options that take in data for all releases. I believe that should be able to handle the markdown footer format structure via a range template.

[miniscruff]

Updating this one more time now that I have some stuff written here #610 which now includes a footer file and format for changelogs which will provide this functionality. No ETA yet but this may be the path forward.