Ignore files created by `\tikzexternalize`

When using TikZ & PGF with:
`\usepackage{tikz} \usetikzlibrary{external} \tikzexternalize`
It creates .dpth and .md5 files for the externalized tikzpictures.

TeX.gitignore

@@ -120,6 +120,10 @@ _minted*
 *.sympy
 sympy-plots-for-*.tex/
 
+# TikZ & PGF
+*.dpth
+*.md5
+
 # todonotes
 *.tdo