Feature: custom filter behaviors

[ancms2600]

I have a list of strings in the format:

`${AccountName} (${AccountId})`

In one case, there were two matches for "L1 Application" but one of them had a hyphen in the account name, which caused it not to match.

I wanted a simple way to sanitize the filter candidate before the match was performed. In my case, I have it remove all non-alphaNumeric characters, like so:

$('#filterByAccount').multiselect({
    enableFiltering: true,
    filterBehavior: ({text}) => text.replace(/[^a-z0-9]+/gi, ' '),
    // ...
});

As a result, it now matches both results, as expected (see image above).

Others could theoretically use this function to do even more, such as modify what is matched on (e.g., starts-with could easily be performed by returning filter candidates that contain starting parts only, and this function could be rotated between a set of possible filter candidate generators depending on the search mode.)

see also: #803 #408