feat: improve how references are displayed

[innocenzi]

This PR improves the way references are displayed. It depends on #18.

Before this PR, references are inserted into backticks to display them as code snippets, and they are separated by a single space.

After this PR, references related to an issue or PR are displayed in a list (with commas and a final "and" word when necessary) and prefixed by "in", and references to a specific commit are displayed in parenthesis.

Three examples of the current behavior is:

• Support for multiple @ parents (@​media, @​supports, etc) #​1161 by @​antfu
• Revert variant apply order in #​1127 #​1162 by @​antfu
• New preflights and minify options a60a0e9b

After this PR, the changelog would look like this:

• Support for multiple @ parents (@​media, @​supports, etc) by @​antfu in #​1161
• Revert variant apply order by @​antfu in #​1127 and #​1162
• New preflights and minify options (a60a0e9b)

This design feels cleaner to me (the 'code snippet' references were attracting too much attention), it's inspired by the way the GitHub-generated release changelog is formatted.

[antfu]

You might need to resolve the conflicts, thanks.

[innocenzi]

@antfu done!