chore: echarts type and add settings property

[SAKURA-CAT]

This pull request includes updates to the swankit library, focusing on versioning, feature additions, and enhancements to the LazySettings class. It also introduces a new unit test for the LazySettings class. Below are the key changes grouped by theme:

Versioning Update:

• Updated the version in pyproject.toml from 0.1.7 to 0.1.8 to reflect new changes.

Feature Additions:

• Added a new chart type, ECHARTS, to the ChartItem enumeration in swankit/core/data.py.
• Introduced a new tags property in the LazySettings class, allowing optional tagging with a setter that enforces immutability after the first assignment. [1] [2]

Enhancements to LazySettings:

• Updated type hints for several properties in LazySettings (exp_colors, description) to make them optional, improving flexibility. [1] [2]

Unit Testing:

• Added a new unit test, test_lazy_settings, in test/unit/core/test_settings.py to validate the behavior of the LazySettings class, including immutability checks for properties.

[Copilot]

Pull Request Overview

A maintenance PR updating versioning, adding new features to the LazySettings class, and extending chart types and unit tests.

• Updated pyproject.toml version to 0.1.8.
• Added a new ECHARTS ChartItem in swankit/core/data.py.
• Enhanced LazySettings by introducing optional type hints and an immutable tags property, with new related unit tests.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
test/unit/core/test_settings.py	Added unit tests for LazySettings immutability behavior using try-except for exception checking.
swankit/core/settings.py	Updated type hints for LazySettings and added a new immutable tags property.
swankit/core/data.py	Introduced a new chart type ECHARTS to the ChartItem enum.
pyproject.toml	Updated version from 0.1.7 to 0.1.8 to reflect the latest changes.