added background setting

chore: update readme image

chore: add image in readme.md

chore: minor changes and improvements to publish in pypi

feat: prepare for first release v0.1.0

feat: add LICENSE, update description in pyproject.toml

feat: add README.md, update pyproject.toml

refactor: minor changes

feat: convert project to pip-installable CLI package

refactor: remove requirements.txt

style: update unicode symbol

feat: add available uncicode character options

feat: add proper logic for month labels alignment in the heatmap

feat: add symbol variable for the unicode heatmap character

style: fix padding issue for the heatmap background