Add folder readme for doc/assets

Includes dependencies for builing the xml_spec LaTeX, as well as running
the trace through the specification.

Author: Thomas Kiley

doc/assets/README.md

@@ -0,0 +1,27 @@
+This folder contains resources for the documentation.
+
+# XML Spec
+
+The folllowing files relate to the specification of the XML trace output when using the `--xml-ui` flag.
+
+## xml_spec.xsd
+The`xml_spec.xsd` file is an XSD specification of the trace. You can validate an
+output xml file from CBMC using the following invocation:
+
+```bash
+$ cbmc --xml-ui main.c | \
+  xmllint --schema xml_spec.xsd --xpath "cprover/result/goto_trace" -
+```
+
+## xml_spec.tex
+
+This is a LaTeX document describing the specification of the trace. It can be compiled to pdf using:
+
+```bash
+$ pdflatex -shell-escape xml_spec.tex
+```
+
+This requires:
+
+ - texlive-latex-base
+ - texlive-latex-extra (for minted package)