Allow specifying an order for changelog types

[about-code]

User Story

In changelogs generated with standard-version the default order of changelog headings for a particular version appears to be alphabetical, ascending . For example Bug Fixes are being rendered before Features. When introducing a new custom type like Deprecation Notices, its commits are being rendered after Bug Fixes but before Features. However, users of my software product or readers of my changelogs may be more interested in features than bug fixes, and want the latter to be listed first.

Feature Request

As a user of standard-version and conventional-changelog I would like to be able to configure a custom order for changelog types, in order to render Features before Bug Fixes before Deprecation Notices (or other custom types).

[about-code]

Related: conventional-changelog/standard-version#293

[trallnag]

Maybe it makes sense to open this issue in the main repo for conventional-changelog