lexer: Accept hyphen and numbers

[sktornado]

Some config names include hyphens and numbers. The wireless config
is one such example.
https://openwrt.org/docs/guide-user/network/wifi/basic

[dmke]

Cool 👍 I'll merge this tomorrow when I'm at my workstation again (and when I've found out why CircleCI doesn't build pull requests...)

[codecov-io]

Codecov Report

Merging #7 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master       #7   +/-   ##
=======================================
  Coverage   68.05%   68.05%           
=======================================
  Files           7        7           
  Lines         695      695           
=======================================
  Hits          473      473           
  Misses        202      202           
  Partials       20       20

Impacted Files	Coverage Δ
lexer.go	89.5% <100%> (ø)	⬆️

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[dmke]

I've merged your changes, thank you.

The wiki states on https://openwrt.org/docs/guide-user/base-system/uci#file_syntax (at the end of the "File Syntax" section):

It is important to know that UCI identifiers and config file names may contain only the characters a-z, 0-9 and _. E.g. no hyphens (-) are allowed. Option values may contain any character (as long they are properly quoted).

So, this leaves me a bit puzzled... Are hypens allowed or are they not? I've glanced a bit over the C sources I did not see an obvious parser function which could tell me the actual syntax allowed.

Do you have time to dig a bit deeper? I don't know when I'm able to to this myself.