[r] Prepare package for CRAN

[immanuelazn]

Description WIP

This pull request prepares the BPCells package for CRAN submission and includes a new release (v0.3.2) with several improvements to documentation, dependencies, and build configuration. The most important changes are grouped below.

Release and CRAN preparation:

• Bumped the BPCells version to 0.3.2 and updated the NEWS.md to reflect the new release and recent changes, including CRAN preparation and documentation improvements.
• Added a LICENSE file with the appropriate copyright and year, as CRAN requires MIT and APACHE files to be in separate places.
• Overall had to rewrite a lot of documentation and moving things around.

Build and CI improvements:

• Updated GitHub Actions workflows (deploy-docs.yml, deploy-full-website.yml, r-test.yml) to use additional R package repositories, improving dependency resolution and adding Bioconductor and BPCells drat as sources.
• Expanded .Rbuildignore to exclude more files and directories from package builds, such as scripts, data-raw, vignettes, and build artifacts.
• Changed configure and configure.win to both use sh instead of bash, for greater compatibility.

Documentation and method improvements:

• Added and improved documentation for S3/S4 methods, particularly for IterableFragments/IterableMatrix, including parameter descriptions and usage examples.
• Vastly expanded IterableMatrix-methods and IterableFragments-methods to cover all S3/S4 methods.
• Added in a bunch of missing or incorrectly named parameter descriptions

Namespace and import/export updates:

• Updated NAMESPACE to import missing functions from graphics, ggplot2, stats, and utils, and to export S3 methods for matrix operations, improving compatibility and compliance with CRAN policies.

Miscellaneous:

• Updated the dummy package license for base directory DESCRIPTION

These changes collectively enhance the package's documentation, build process, and CRAN compatibility, while also improving maintainability and user experience.