v3.5.0+3

This revision updates documentation, improves the build system, and refines examples and tests.
For the full changelog, see: c00115d

• Update all information in README.md
• Split README.md and extract consumption info to PACKAGE-README.md
• Add testscript files for all tests to hide console output
• Ensure NDEBUG macro is not defined in smoke test
• Fix unintended import of Catch2 in examples package (see #3)
• Update directory-based symlinks to simplify buildfile structures
• Declare directory-based symlinks in .gitignore/.gitattributes
• Remove unnecessary .gitignore files
• Transform function_types_stateless.hpp.orig back into symlink
• Use robust and generic handling of patches in sol2/sol2/buildfile
  and remove unnecessary target-specific variable assignments
• Add missing examples from docs and tutorials to examples package
• Add customization example to the examples package
• Remove interop examples from examples package
  that require unavailable external dependencies
• Remove empty and unnecessary require_dll_example and customization
  targets from basic/buildfile in the examples package
• Simplify loop over sources in sol2-examples/basic/buildfile
• Use robust flattening of example paths to generate unique
  executable names in the sol2-examples/basic/buildfile loop
• Move default config of sol2-examples package back to root.build
• Use robust flattening of test paths to generate unique
  executable names in the sol2-tests/tests/buildfile loop
• Remove utility tests (depend on broken run_time tests)
• Switch to liblua ^5.4.8 in the testing section for Lua import