Allow filtering to reduce the total number of languages listed

[westonruter]

From a plugin review by @SvenWoltmann:

It would be great if one could select a subset of the available languages for the dropdown, so you don’t always have to scroll through all 185 languages.

[westonruter]

This could be achieved by adding a PHP WP filter to the get_language_names() function:

syntax-highlighting-code-block/syntax-highlighting-code-block.php

Lines 432 to 439 in e674f52

	/**
	* Language names.
	*
	* @return array Mapping slug to name.
	*/
	function get_language_names() {
	return require __DIR__ . '/language-names.php';
	}

[allejo]

This could probably be merged in with functionality for #191

[westonruter]

Ah yes, of course.

[avillegasn]

I'd like the related PR to be merged. Having the filter syntax_highlighting_code_block_language_names is a nice feature.

[westonruter]

The scope of the related PR is too large and there are aspects which I don't think are needed. The scope should be reduced down to just fix the issue of reducing the total number of languages.

Also, there is perhaps a better approach that could be taken than just to filtering the language names. Perhaps it could reuse the syntax_highlighting_code_block_auto_detect_languages filter so that only those languages are listed in the dropdown as well as being used for auto-detection. I don't think it really makes a lot of sense to have languages listed if they're never going to be used for auto-detection. In that case, perhaps the filter should be renamed to just syntax_highlighting_code_block_languages with the old filter deprecated.

[avillegasn]

I agree with your proposal. In fact, at first I expected the syntax_highlighting_code_block_auto_detect_languages to filter the languages from the list too. It makes sense to only have the syntax_highlighting_code_block_languages filter.