feat: add mdbook plugin for testing mun code in book

[legendiguess]

This pull request add mdbook plugin that's test all mun code(indicated by keyword mun before code block).

Also, plugin allows to specify "testing method" for each code block by using keywords no_run, compile_fail and skip.
Example: mun,no_run, mun,compile_fail and etc

With this pull request, plugin already setted as dependency for mun book, so before building new version of book by mdbook build one need to compile mdbook-mun-examples-test crate and add it's executable file to environment variables.

closes #209

[legendiguess]

Also need to mention that this pr skip testing one code from chapter 2.2 Functions because it's have a bug right now - #262

[codecov]

Codecov Report

Merging #263 into master will decrease coverage by 0.27%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #263      +/-   ##
==========================================
- Coverage   79.10%   78.82%   -0.28%     
==========================================
  Files         219      220       +1     
  Lines       13024    13070      +46     
==========================================
  Hits        10303    10303              
- Misses       2721     2767      +46     

Impacted Files	Coverage Δ
crates/mun_mdbook_test_plugin/src/main.rs	0.00% <0.00%> (ø)

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[Wodann]

Nice work @legendiguess. Very happy with this addition. I've added some minor remarks, but mostly it looks good to go.

Could you also remove book/listings/ch03-structs/mun.exe? It's not necessary to have that committed 🙂

[Wodann]

@legendiguess I see that you performed a merge. In the future, please do "rebase merges" instead. If you are unfamiliar with rebase merges, our contributing guidelines explain it in more detail here.

[legendiguess]

@legendiguess I see that you performed a merge. In the future, please do "rebase merges" instead. If you are unfamiliar with rebase merges, our contributing guidelines explain it in more detail here.

Oh, sorry, it's was just due to my inexperience, i removed merge 👍

[Wodann]

@legendiguess Do you need any help to fix the last couple of issues?

[Wodann]

That looks a lot better. I recommended a few changes, because:

• I think we should use no_run instead of run. I explained why in one of the comments in main.rs
  This means that by default, we always run the Mun source code, unless you specify no_run.
• After looking at our CLI source code, it seems that just using pub fn main as the entry point for Mun source is the best option. That's the same for our mdbook plugin and the Mun CLI then.
• I think we don't need skip anymore, now that the compiler bug is fixed.
• I think compile_fail should always mean that nothing will run.

[Wodann]

Suggested change

	```mun,ignore
	```mun

[Wodann]

This should compile if you convert return bar + 3; into return 3;, I think

[legendiguess]

Shouldn't it be a separate pr?