rust-lang/rust-clippy#12133

    warning: function cannot return without recursing
       --> src/map.rs:276:5
        |
    276 | /     fn eq(&self, other: &Self) -> bool {
    277 | |         self.map.eq(&other.map)
    278 | |     }
        | |_____^
        |
    note: recursive call site
       --> src/map.rs:277:9
        |
    277 |         self.map.eq(&other.map)
        |         ^^^^^^^^^^^^^^^^^^^^^^^
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unconditional_recursion
        = note: `-W clippy::unconditional-recursion` implied by `-W clippy::all`
        = help: to override `-W clippy::all` add `#[allow(clippy::unconditional_recursion)]`

Fixed a spelling error in the second paragraph of the README file.

- Changed "exponet" to "exponent"

fix: Correct spelling error

Handle Unexpected::Unit in Error::invalid_value

Format f64 in error messages using ryu