common/travis/xlint.sh: print Github annotations

Turns xlint, version lint, and commit lint messages into warning or error
annotaions. All are printed with special highlighting in the action log and
summary. Xlint and version lint annotations are shown inline in the changes tab
and commit view. Annotations without line number are shown at line 1.

common/scripts/lint2annotations.awk

@@ -0,0 +1,11 @@
+# Converts xlint/etc format lints into GH Actions annotations
+# The original line is printed alongside the annotation command
+{
+	split($0, a, ": ")
+	split(a[1], b, ":")
+	msg = substr($0, index($0, ": ") + 2)
+	if (b[2]) {
+		line = ",line=" b[2]
+	}
+	printf "::error title=Template Lint,file=%s%s::%s\n", b[1], line, msg
+}