Allow custom default export directory by config

[dark-person]

Changes (New Feature)

• Use koanf as config package
• Allow user to define default export folder by config.yaml
• Update gitignore and docs

Related Issues

This change can solve 1st part of issue #58.

Checklist:

Code Checklist:

• I have run the new code and ensure the change is work expected
• I have write/modify comments to important function & hard-to-understand code
• I have checked my code has no misspellings & no warnings
• I have checked that only essential code remains in this pull request

Documentation Checklist:

• I have add new feature description to README.md of this repository
• I have add/modify file description to README.md of the package (tick if not applicable)

Testing Checklist:

• I have create new test case / test for new feature
• I have run all new & existing test and pass locally with my changes