feat: add the prefix option to prepend a path to all URLs

[Angelmmiguel]

Introduce a new --prefix option to preped a string to all URLs (workers and static assets). This option receives a string that will be properly normalized by the application. If no option is provided, the default value will be "" (no prefix).

This is the outcome from the --help command:

~/W/o/webassembly-functionless ❯❯❯ cargo run -- --help

Wasm Workers Server is a blazing-fast self-contained server that routes HTTP requests to workers in your filesystem. Everything run in a WebAssembly sandbox

Usage: wws [OPTIONS] [PATH]

Arguments:
  [PATH]  Folder to read WebAssembly modules from [default: .]

Options:
      --host <HOSTNAME>  Hostname to initiate the server [default: 127.0.0.1]
  -p, --port <PORT>      Port to initiate the server [default: 8080]
      --prefix <PREFIX>  Prepend the given path to all URLs
  -h, --help             Print help information
  -V, --version          Print version information

Note that this string must use URI format (/X/Y) because it's not a filesystem path. However, I also considered the case that someone introduces a windows path (\X\Y). I considered it because it's easy to implement, but I may drop support in the future.

It closes #31

[assambar]

Ship it!