Rust: Broken highlighting of escape sequences in char literals

[mattgodbolt]

monaco-editor version: 0.24.0
Browser: Chrome
**OS:**Linux

Rust char literals containing an escape sequence such as '\n' don't get highlighted correctly and '"' even breaks highlighting of the following code:

pub fn foo() {
    let _works_in_str = "\n\"";
    let _x = '\n';
    let _y = '\"';
    // Now it thinks everything until the next
    // double quote is part of a string
}

pub fn bar() {
    let _unbreak_it = "\"\"";
    let _and_here_it_works_again = true;
}

Pasting this into https://microsoft.github.io/monaco-editor/ and selecting 'Rust' reproduces the issue.

See compiler-explorer/compiler-explorer#2665

[alexdima]

We are more than welcoming a PR by the community!