Font locking (syntax highlighting) doesn't work with keywords starting with a number #581

Expected behavior

The following are both valid keywords, however, the font locking doesn't work on the second one

:foo
:1foo 

Actual behavior

Keywords starting with a number are not colorised as keywords

Steps to reproduce the problem

see example above

Environment & Version information

clojure-mode version

Include here the version string displayed by M-x clojure-mode-display-version. Here's an example:

clojure-mode (version 20201126.1558)
clojure-mode (version 5.13.0-snapshot)

Emacs version

GNU Emacs 27.1

Operating system

Mac OS 11.1