Add pyproject.toml and bundle fonts

[Dando18]

Adds a pyproject.toml to make installing the plotting library in a virtualenv and using it easier.

Also distributes the font directly in the package, so no quirky path is needed.
If not found for some reason, then it falls back to system font or user supplied font.

[Copilot]

Pull Request Overview

This PR adds Python packaging configuration and bundles fonts with the library to simplify installation and usage. The changes eliminate the need for users to manually specify font paths by automatically discovering bundled or system fonts with appropriate fallbacks.

Key changes:

• Added pyproject.toml with project metadata, dependencies, and build configuration
• Implemented font resolution logic that searches for bundled fonts, system fonts, and falls back to defaults
• Updated README to remove the explicit font_path parameter from the usage example

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 1 comment.

File	Description
pyproject.toml	Defines packaging configuration, dependencies, and project metadata for distribution
pssgplot/pssgplot.py	Refactored font handling with new _resolve_font method that searches bundled and system fonts
README.md	Simplified usage example and added installation instructions

Comments suppressed due to low confidence (1)

README.md:9

• Corrected spacing in 'Aquick' to 'A quick'.

A quick demo of plotting a simple bar chart:

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[Copilot]

The bundled font path is incorrect. According to pyproject.toml line 50, fonts are packaged inside the pssgplot package (pattern pssgplot = ["*.ttf", "fonts/*.ttf"]), but this code looks for them at parent.parent / "fonts", which would be outside the package. The path should be Path(__file__).parent / "fonts" / "gillsans.ttf" to correctly locate fonts within the pssgplot package directory.

Suggested change

	bundled_font_path = Path(__file__).parent.parent / "fonts" / "gillsans.ttf"
	bundled_font_path = Path(__file__).parent / "fonts" / "gillsans.ttf"