Ignore *.auxlock files created by TikZ in TeX

TikZ uses *.auxlock files to check if the main *.aux file is available.
This is only used when using the external tikz library.

TeX.gitignore

@@ -123,6 +123,7 @@ sympy-plots-for-*.tex/
 # TikZ & PGF
 *.dpth
 *.md5
+*.auxlock
 
 # todonotes
 *.tdo