Add a vignette of creating an R package

[yutannihilation]

Fix #74

Simple version of my blog post, https://yutani.rbind.io/post/2021-06-06-unofficial-introduction-to-extendr-1-your-first-r-package-with-rust/. I guess the original one is a bit too casual to turn into the vignette, so I tweaked a bit.

Note that I turned all R chunk to static with pre-executed results pasted. Of course I can create R package on the tempdir and generate the output lively, I'm a bit afraid it becomes a problem on CRAN check.

[Ilia-Kosenkov]

Overall this looks good. However, the language needs a little bit of polishing. I'd say, a review by a native speaker or someone living long enough in the English-speaking environment would be good.

I also suggest to make separate PRs for runtime Rust code execution (using rust_function, etc.) and for markdown, i.e. what to write in the .Rmd to get access to Rust, similar to what is written in the README.Rmd.

[yutannihilation]

I'd say, a review by a native speaker or someone living long enough in the English-speaking environment would be good.

I agree. My English is not good enough for writing documents like this.

i.e. what to write in the .Rmd to get access to Rust

Isn't rmarkdown.Rmd the one for this (though it doesn't refer to functions like rust_function())?

[yutannihilation]

Thank you for the thorough review! I reflected the comments.

[clauswilke]

Looks good to me. Please go ahead and merge whenever you're ready.

[yutannihilation]

Thanks, I'll keep this open for a while to proofread this once again, and then merge.

[clauswilke]

I think we shouldn't let minor stylistic issues get in the way of producing useful content. It's good enough as is, and I'd suggest you just go ahead and merge. I can do an additional round of copy-editing afterwards also.

[yutannihilation]

Thanks, I'm merging this.