Add iterator pattern.

[ilopX]

Template Method Pattern

Iterator is a behavioral design pattern that lets you traverse elements of a collection without
exposing its underlying representation (list, stack, tree, etc.).

Tutorial: here.

Diagram:

Client code:

void main() async {
  final GitHubRepo gitHubRepo = await GitHubLoader.get(
    userName: 'RefactoringGuru',
    repoName: 'design-patterns-dart',
  );

  print(
    'Iterate last 10 commits.'
        '\n----------------------------',
  );

  for (Commit commit in gitHubRepo.commitIterator()) {
    print(commit.message);
  }
}

Output:

Iterate last 10 commits.
----------------------------
Merge pull request #74 from ilopX/fix-conceptual-command-pattern-folder-name Fix conceptual command pattern folder name
Fix conceptual command pattern folder name.
Merge pull request #73 from ilopX/add-conceptual-command-pattern Add conceptual command pattern
Bump version 0.35.0.
Add README.
Impl conceptual command pattern.
Merge pull request #72 from ilopX/add-singleton-pattern Add singleton pattern.
Bump version 0.34.0.
Add README.