docs: add more comments to example code in readme

Author: natecraddock

readme.md

@@ -55,13 +55,16 @@ const ziglua = @import("ziglua");
 const Lua = ziglua.Lua;
 
 pub fn main() anyerror!void {
+    // Create an allocator
     var gpa = std.heap.GeneralPurposeAllocator(.{}){};
     const allocator = gpa.allocator();
     defer _ = gpa.deinit();
 
+    // Initialize the Lua vm
     var lua = try Lua.init(allocator);
     defer lua.deinit();
 
+    // Add an integer to the Lua stack and retrieve it
     lua.pushInteger(42);
     std.debug.print("{}\n", .{try lua.toInteger(1)});
 }