Cleanup code block tags

[alexkazik]

Since the code blocks in the readme often do not compile anyway due to removing the comments, the extra tags are probably not helpful and can be removed/replaced.

Suggestion: when a code block is identified as rust (is_rust_code_block) then remove all tags and replace it with "rust".

Should probably optional or possible to switch off. Also someone may want to have another tag (including the empty string).

[orium]

It already does that. It strips tags that only have meaning for rustdoc. For instance if you have

//! ```should_panic
//! fail!("foo");
//! ```

cargo-rdme generates this README:

```rust
fail!("foo");
```

This stuff is tested here:

cargo-rdme/src/transform/rust_markdown_tag.rs

Line 321 in 4191ebb

fn test_markdown_tag_for_known_code_block_tags() {

If this is not what you mean, please give a concrete example.

[alexkazik]

Yes it does. I'm very sorry. For whatever reason I used "rust,no_compile" (and not ignore, I have no idea where I picked that up).

Interestingly enough the rust doc does what I want: do rust syntax highlight and not show a "untested" badge next to it (as ignore does).

[orium]

It seems no_compile is not currently a thing in rustdoc, but it seems it might become one: rust-lang/rust#96573

When it does I'll update cargo-rdme to support that.