Define concourse-pipeline-yaml language id

vscode-extensions/vscode-concourse/scripts/preinstall.sh

@@ -1,5 +1,11 @@
 #!/bin/bash
 set -e
+# Download yaml TextMate grammar
+curl https://raw.githubusercontent.com/textmate/yaml.tmbundle/master/Syntaxes/YAML.tmLanguage > yaml-support/yaml.tmLanguage
+
+# Preinstall commons-vscode package
 (cd ../commons-vscode ; npm install)
 npm install ../commons-vscode
+
+# Use maven to build fat jar of the language server
 ../mvnw -U -f ../pom.xml -pl vscode-concourse -am clean install