Rollup merge of rust-lang#74135 - ehuss:update-books, r=ehuss

Update books

## book

3 commits in 4e7c00bece1544d409312ec93467beb62b5bd0cb..84a31397b34f9d405df44f2899ff17a4828dba18
2020-06-19 09:39:12 -0400 to 2020-07-04 10:50:18 -0500
- Update Windows install instructions (rust-lang/book#2389)
- Update ch01-02-hello-world.md (rust-lang/book#2386)
- bump mdbook version in github action (rust-lang/book#2380)

## reference

2 commits in 04d5d5d7ba624b6f5016298451f3a63d557f3260..0ea7bc494f1289234d8800bb9185021e0ad946f0
2020-06-16 15:08:05 -0700 to 2020-07-02 15:33:04 -0700
- Fix mis-capitalization of type name. (rust-lang/reference#844)
- Fix name of trait for array indexing. (rust-lang/reference#840)

## embedded-book

1 commits in 616962ad0dd80f34d8b802da038d0aed9dd691bb..94d9ea8460bcbbbfef1877b47cb930260b5849a7
2020-06-23 16:03:45 +0000 to 2020-07-05 14:17:40 +0000
- Note on transformation of static variables by attribute exception  (rust-embedded/book#251)

## rust-by-example

1 commits in 6f94ccb48da6fa4ed0031290f21411cf789f7d5e..229c6945a26a53a751ffa4f9cb418388c00029d3
2020-06-20 17:51:30 -0300 to 2020-07-06 10:13:15 -0300
- Modify comments (rust-lang/rust-by-example#1359)