This release represents a big update to the book. The main objective of this release is to update all code examples in the book to Zig 0.16. This includes:

• update Chapter 9 (Build System) and Chapter 15 (Image filter project) to include the latest changes in the Zig build system. Many methods from std.Build.Step and std.Build.Compile were moved to other places.
• update _char_index() method on the Base64 project to fix issue reported at #185.
• fix issue reported at #191 .
• with the introduction of the new io argument in many I/O related functions in the Zig Standard Library, this PR also updates many code examples scattered across the book to account for this new argument.
• add a new section in Chapter 13 (Filesystem and I/O) to describe this new io argument in the Zig I/O interface.
• many code examples from chapter 13 were not being actively compiled during the book compilation process. This PR also fixes this.
• with the new I/O interface, the std.net module was completed removed in favor of std.Io.net, and this changed completely how network operations are made in Zig. This affected mainly the HTTP server project. So, this PR also updates Chapter 7 to account for this big update.