Add doc comment to fetchAndAddDependencies

Author: antlilja

src/Package.zig

@@ -214,6 +214,18 @@ pub fn getName(target: *const Package, gpa: Allocator, mod: Module) ![]const u8
 
 pub const build_zig_basename = "build.zig";
 
+/// Fetches and adds dependencies to pkg
+///
+/// dependencies_source contains source code for the imports in the generated dependencies.zig:
+/// pub const some_lib = @import("HASH");
+/// pub const some_other_lib = @import("HASH");
+/// ...
+///
+/// build_roots contains source code for the build roots in the generated dependencies.zig:
+/// pub const some_lib = "~/.cache/zig/p/HASH";
+/// pub const some_other_lib = "~/.cache/zig/p/HASH";
+/// pub const some_non_zig_lib = "~/.cache/zig/p/HASH";
+/// ...
 pub fn fetchAndAddDependencies(
     pkg: *Package,
     deps_pkg: *Package,