Config file documentation

[smasongarrison]

This pull request primarily updates and extends documentation for the {ggpedigree} package, focusing on improving clarity, adding examples, and enhancing the user experience. The most significant changes include renaming and revising the configuration vignette to better describe its purpose, refining explanations and visual previews, and updating references to advanced examples in both R Markdown and HTML documentation. Additionally, a new vignette is introduced to demonstrate basic configuration usage.

Documentation improvements and content updates:

• Renamed and revised the configuration vignette from vignettes/articles/v02_configuration.Rmd to vignettes/articles/v11_configuration_extended.Rmd, updating the title and index entry to clarify that it covers more uses of the config argument for controlling ggpedigree plots.
• Updated explanations in the configuration vignette for clarity, including concise guidance on the config argument and its usage in plotting functions.
• Changed the value of code_unknown in the configuration example from 0 to 3, reflecting an updated convention for unknown sex codes in pedigree plots.
• Enhanced the emoji shapes section by adding a preview image (emoji_preview.png) and clarifying the differences in font rendering between preview and saved PNG outputs.
• Added a new vignette file vignettes/v10_configuration.R to demonstrate setup, library usage, and basic pedigree plotting with the Potter dataset.

Reference and formatting updates:

• Updated references to advanced examples in both vignettes/v00_plots.Rmd and vignettes/v00_plots.html to indicate that these are available online to reduce package file size, improving the documentation’s clarity and relevance. [1] [2]
• Minor formatting changes in plot scale comments for better readability in HTML output.

These changes collectively make the documentation more user-friendly, accurate, and visually informative, especially for new users learning to configure and customize pedigree plots.