refactor(changelog): sort commits by newest in CHANGELOG

Previously, cliff was sorting the commits by oldest first.
Like:

```
 - Support parsing the missing scopes with `default_scope` (orhun#8)
 - Support generating a changelog scoped to a directory (orhun#11)
```

As the PR numbers indicate, the first bullet point is definitely
older than the latter.

With this update, it will look like this:
```
 - Support generating a changelog scoped to a directory (orhun#11)
 - Support parsing the missing scopes with `default_scope` (orhun#8)
```

Signed-off-by: Taylan Dogan <[email protected]>

git-cliff/src/lib.rs

@@ -145,7 +145,7 @@ pub fn run(mut args: Opt) -> Result<()> {
 	for git_commit in commits.into_iter().rev() {
 		let commit = Commit::from(&git_commit);
 		let commit_id = commit.id.to_string();
-		releases[release_index].commits.push(commit);
+		releases[release_index].commits.insert(0, commit);
 		if let Some(tag) = tags.get(&commit_id) {
 			releases[release_index].version = Some(tag.to_string());
 			releases[release_index].commit_id = Some(commit_id);