Modernize shinymaterial package for 2025

[ericrayanderson]

• Update DESCRIPTION with modern dependencies:

  • shiny >= 1.7.0 (was >= 0.7.0)
  • Add rlang (>= 1.0.0) and cli for modern error handling
  • Add testthat (>= 3.0.0) to Suggests
  • Update RoxygenNote to 7.3.2 with markdown support
  • Add BugReports URL

• Security improvements:

  • Replace eval() with Function() constructor in JS handler
  • Add try/catch error handling for safer code execution

• Modernize error handling:

  • Replace message("ERROR: ...") with cli::cli_abort()
  • Use structured error messages with cli formatting

• Update JavaScript to ES6+ patterns:

  • Replace $(document).ready() with DOMContentLoaded
  • Use ES6 class syntax for Shiny.InputBinding
  • Add 'use strict' and JSDoc comments
  • Use const/let instead of var
  • Use arrow functions where appropriate

• Remove deprecated code:

  • Remove dir_recursion() utility (replaced with dir.create recursive)
  • Use built-in dir.create(..., recursive = TRUE)

• Add CI/CD infrastructure:

  • Add GitHub Actions R-CMD-check workflow
  • Add GitHub Actions test-coverage workflow
  • Add testthat testing infrastructure with initial tests

• Update .Rbuildignore for new files

• Update NAMESPACE with cli and rlang imports