feat: random_str/src/lib.rs now includes content of its README.md - good for docs.rs

[peter-lyons-kehl]

Now rustdoc, docs.rs (and probably rust-analyzer-generated docs in IDE mouseovers/tool tips) include and render content README.md.

Side note 1: I see two README.md files. Suggest having just one, and using a symlink from the other location. That may not completely work for developers on Windows, but they can workaround.

Side note 2: both README.md files link to LICENSE, which doesn't exist. EDIT: That's because I made random_str/random_str/src/lib.rs include ../README.md, which is the copy under random_str/random_str and not under the root random_str/. Suggest adding a symlink for LICENSE - I'm happy to add that to this pull request.

Side note 3: Suggest considering dual licensing under Apache-2.0 OR MIT, as is common in Rust ecosystem. (rand does that, too.) Or even triple licensing under Apache-2.0, MIT and BSD (my prudent-rs/prudent or its sister crate (about to be born/named) is going to depend on random_str, and I triple license). For that you could use license = "BSD-2-Clause OR Apache-2.0 OR MIT".

[peter-lyons-kehl]

random_str/random_str on  main [!] is 📦 v1.1.0 via 🦀 
❯ cargo +1.85.1 rustdoc 
    Checking cfg-if v1.0.4
    Checking rand_core v0.10.1
    Checking libc v0.2.186
    Checking cpufeatures v0.3.0
    Checking chacha20 v0.10.0
    Checking getrandom v0.4.2
    Checking rand v0.10.1
 Documenting random_str v1.1.0 (/share/pkehl/GIT/random_str/random_str)
warning: unresolved link to `LICENSE`
   --> random_str/src/lib.rs:3:1
    |
3   | / //! This crate provides a set of functions to generate random strings, numbers, letters, symbols and bool...
4   | | pub mod random {
5   | |     use rand::{
6   | |         distr::uniform::{SampleRange, SampleUniform},
...   |
122 | |     ///     .build();
123 | |     /// let random_phone_number = format!("+52 {}", digits.unwrap());
    | |_____________________________________________________^
    |
    = note: the link appears in this line:
            
            This project is licensed under the MIT license. See the [LICENSE](LICENSE) file for more information.
                                                                              ^^^^^^^
    = note: no item named `LICENSE` in scope
    = help: to escape `[` and `]` characters, add '\' before them like `\[` or `\]`
    = note: `#[warn(rustdoc::broken_intra_doc_links)]` on by default

warning: `random_str` (lib doc) generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 7.34s
   Generated /share/pkehl/GIT/random_str/target/doc/random_str/index.html

[DeimosHall]

Thanks again. I'm fine with your suggestions, feel free to remove one readme, creating the symlinks and adding the triple licensing.