Make global binary

```
$ cargo install html_parser
    Updating crates.io index
  Downloaded html_parser v0.7.0
  Downloaded 1 crate (54.8 KB) in 0.62s
error: there is nothing to install in `html_parser v0.7.0`, because it has no binaries
`cargo install` is only for installing programs, and can't be used with libraries.
To use a library crate, add it as a dependency to a Cargo project with `cargo add`.
```