Add proper XML encoding handler

[mhxion]

Fix #30

Add an inner function that retrieves XML encoding information from XML declaration line (if exists) and pass it to open() so it decodes the XML properly.

• Code is properly commented with needed references
• Code style and formatting has been kept as it is seen on the original codebase (e.g., no type checking has been added)

Local workflow execution tests:

[mhxion]

I also applied for a working student position at Knime with this PR, if it makes any difference.

[mhxion]

Squashed the last commits (as the last commit was just cleaning up syntax formatting) as suggested by @steffen-fissler. Although this required a force-push, an alternative would've been using the GitHub squash feature before accepting the pull request, I think in this case it doesn't affect the public repository.