Mypy fixes, and improvements to the InteractiveParser API

What's Changed

• Add test cases for tree templates by @plannigan in #1096
• 🖊 Fix Typo: plural "options" instead of singular "option" by @hf-kklein in #1101
• PEP 8: Minor Code Style Improvements by @hf-kklein in #1102
• Add Code Style Section to Contribution Guide by @hf-kklein in #1107
• Fix MyPy Warnings in lark/tools/init.py by @hf-kklein in #1100
• rename n to child when iterating over children by @hf-kklein in #1110
• specify ignored mypy error by using type: ignore[error] in lark/tree.py and lark/utils.py by @hf-kklein in #1099
• Add py.typed to package_data of lark package by @hf-kklein in #1109
• InteractiveParser: Added iter_parse() method, for easier instrumentation by @erezsh in #1111

New Contributors

• @hf-kklein made their first contribution in #1101

Full Changelog: 1.1.0...1.1.1