enh(bash) $pattern: allow numbers after the first character (#3494)

* Update the pattern regex for the bash language

Fixes: #3489 ((bash) keywords with numbers are not recognized)

With the new regex, also numbers INSIDE the pattern is allowed. Before, `a2enmod` would not have been recognized. Now it gets properly recognized.

For the details of the test results see: #3489 (comment)

Author: mmattel

CHANGES.md

@@ -10,6 +10,7 @@ New Grammars:
 
 Grammars:
 
+- enh(bash) improved keyword `$pattern` (numbers allowed in command names) [Martin Mattel][]
 - fix(markdown) Handle `***Hello world***` without breaking [Josh Goebel][]
 - enh(php) add support for PHP Attributes [Wojciech Kania][]
 - fix(java) prevent false positive variable init on `else` [Josh Goebel][]
@@ -22,7 +23,7 @@ Grammars:
 - enh(elixir) recognize references to modules [Mark Ericksen][]
 - enh(css): add support for more properties [Nicolaos Skimas][]
 
-
+[Martin Mattel]: https://github.com/mmattel
 [John Foster]: https://github.com/jf990
 [Wojciech Kania]: https://github.com/wkania
 [Melissa Geels]: https://github.com/codecat

src/languages/bash.js

@@ -355,7 +355,7 @@ export default function(hljs) {
     name: 'Bash',
     aliases: [ 'sh' ],
     keywords: {
-      $pattern: /\b[a-z._-]+\b/,
+      $pattern: /\b[a-z][a-z0-9._-]+\b/,
       keyword: KEYWORDS,
       literal: LITERALS,
       built_in: [