Add support for full_info_string render option

[digitalmoksha]

Add support for an option, full-info-string, that cmark-gfm supports which allows anything beyond the language specifier on a code block to be added as the data-meta attribute.

Related to #275

[digitalmoksha]

@kivikakk I didn't realize until looking through the current PRs (after I wrote this, of course) that #257 is very similar. Mine doesn't pass the information into the syntax highlighter plugin, and implements an option that mirrors cmark-gfm

Feel free to use one or the other, or something blended.

[digitalmoksha]

Really struggling with the CI failure, https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058

---- src/parser/mod.rs - parser::ComrakRenderOptions::full_info_string (line 403) stdout ----
[656](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:657)
Test executable failed (exit status: 101).
[657](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:658)

[658](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:659)
stderr:
[659](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:660)
thread 'main' panicked at 'assertion failed: `(left == right)`
[660](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:661)
  left: `"<pre><code data-meta=\"extra info\" class=\"language-rust\">fn hello();\n</code></pre>\n"`,
[661](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:662)
 right: `"<pre><code class=\"language-rust\" data-meta=\"extra info\">fn hello();\n</code></pre>\n"`', src/parser/mod.rs:10:1
[662](https://github.com/kivikakk/comrak/actions/runs/4028558812/jobs/6925581058#step:4:663)

The order of the attributes on the generated HTML seems to change back and forth. I had even tried to add an additional test, one with github_pre_lang set

    ///
    /// options.render.full_info_string = true;
    /// options.render.github_pre_lang = true;
    /// assert_eq!(markdown_to_html("``` rust extra info\nfn hello();\n```\n", &options),
    ///            "<pre data-meta=\"extra info\" lang=\"rust\"><code>fn hello();\n</code></pre>\n");

and no matter what order I placed the data-meta, it always failed on one of the tests.

In ruby I could just do an expect(markdown_to_html(...)).to include("data-meta=\"extra info\"") and be done with it. Don't know how to achieve that in Rust yet.

[digitalmoksha]

I fixed the test problem I was having. So it looks like everything passes, except for the problem with extensions.txt that was mentioned here

[kivikakk]

Thank you very much — this is very clean, and #257 can happily be implemented in terms of this.

I'm going to hackily adjust CI so the footnote issues stop making tests red, then I'll rebase and merge this.