build: improve git-cliff CHANGELOG output

[dundargoc]

• Sort sections according to custom preference instead of
  alphabetically. It is ordered according to "most relevant" to "least
  relevant" to users.
• Sort commits alphabetically
• Don't uppercase the first letter of the commit message

[dundargoc]

Changelog on master: https://gist.github.com/dundargoc/fcee4fef909543c17962f3cc40e35013
Changelog between 0.9.4 and 0.9.5: https://gist.github.com/dundargoc/aac6e037e7179b62fcf53308c8afd04a

[teto]

Impressive, The Vim patches section contains a bit of junk (abcde89 and so on), I dont know if that was there before or not.

[dundargoc]

Impressive, The Vim patches section contains a bit of junk (abcde89 and so on), I dont know if that was there before or not.

It contains junk because the commit messages are junk. The commit message vim-patch:02774f99cebc will show up as 02774f99cebc. It was not there before as vim-patch commits were not included before.