Merge pull request #37 from internalsystemerror/1.8.x

Add libxml2-utils to allow use of xmllint

Author: geerteltink

Dockerfile

@@ -16,6 +16,7 @@ RUN apt update \
     && ACCEPT_EULA=Y apt install -y \
         git \
         jq \
+        libxml2-utils \
         libzip-dev \
         npm \
         sudo \

README.md

@@ -236,6 +236,8 @@ The container provides the following tools:
 
   Consumers can provide their own rules via a [.markdownlint.json](https://github.com/DavidAnson/markdownlint-cli2#markdownlintjsonc-or-markdownlintjson) file.
 
+- A `xmllint` binary, via the [libxml2-utils](https://packages.debian.org/stretch/libxml2-utils) package.
+
 - A `yamllint` binary, via the [adrienverge/yamllint](https://github.com/adrienverge/yamllint) package.
 
 - The [jq](https://stedolan.github.io/jq/) command, a CLI JSON processor.