Scriptgen

- Fixed multiple new lines in Windows.
- Added more C templates.

- Added XML templates.

- Added index parameter in filter_func.
- Changed from current working path to file directory path in `gen_docs.py` script.

- Added default values for the builder classes.
- Added optional parameters.
- Exposed `CSharpBlockBuilder` class in `scriptgen.templates.csharp` package.
- Bug fixes.

- Added `IndentType`, `StringBuilder`, and `BlockBuilder` classes.
- Added `diff_lines`, `diff_text`, `interpolate_text`, `timestamp`, and `write_text_file` utility methods.
- Added C and Markdown templates.
- Added tests for the utility methods, C templates, and Markdown templates.
- Added `gen_docs.py` script and template files.