mdBook: update to 0.4.20.

srcpkgs/mdBook/template

@@ -1,6 +1,6 @@
 # Template file for 'mdBook'
 pkgname=mdBook
-version=0.4.18
+version=0.4.20
 revision=1
 build_style=cargo
 short_desc="Create book from markdown files. Like Gitbook but implemented in Rust"
@@ -9,7 +9,7 @@ license="MPL-2.0"
 homepage="https://github.com/rust-lang/mdBook"
 changelog="https://raw.githubusercontent.com/rust-lang/mdBook/master/CHANGELOG.md"
 distfiles="https://github.com/rust-lang/mdBook/archive/v${version}.tar.gz"
-checksum=ce357327f4443189fde307103f8008f43410ca8b738c5c61401ada9a54b8b5b5
+checksum=b6fe12979334132b35bb8478a236ef7c8684ce7959b1835268e463581d9af490
 
 post_install() {
 	vlicense LICENSE