Allow hyphen in language name

[zeripath]

Highlight js has a language class jboss-cli that we will currently sanitize away.

We should allow hyphens in markdown code block names.

[guillep2k]

How about digits?

EDIT: \w already includes digits. (word characters (≡ [0-9A-Za-z_]))

[codecov-io]

Codecov Report

Merging #9873 into master will decrease coverage by 0.04%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master    #9873      +/-   ##
==========================================
- Coverage   42.32%   42.27%   -0.05%     
==========================================
  Files         604      604              
  Lines       79155    79228      +73     
==========================================
- Hits        33504    33496       -8     
- Misses      41523    41603      +80     
- Partials     4128     4129       +1

Impacted Files	Coverage Δ
routers/user/auth.go	11.44% <0%> (-0.59%)	⬇️
modules/setting/setting.go	45.09% <0%> (-0.44%)	⬇️
modules/graceful/server.go	48.55% <0%> (-3.8%)	⬇️
services/pull/check.go	54.54% <0%> (-4.2%)	⬇️
modules/process/manager.go	74.69% <0%> (-3.62%)	⬇️
modules/log/event.go	64.61% <0%> (-1.03%)	⬇️
models/error.go	30.76% <0%> (-0.55%)	⬇️
models/repo.go	47.02% <0%> (-0.13%)	⬇️
models/gpg_key.go	55.59% <0%> (+0.55%)	⬆️
services/pull/patch.go	67.92% <0%> (+1.25%)	⬆️
... and 1 more

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