Update to support persistent config/localStorage filters

[gmt4]

This attempts to address #4 to provide two types of filters: 1) filters defined in settings.php, and, also provide 2) localStorage filters.

Works as far as I've been using it, but probably could be reworked to be cleaner/prettier.

[mbolli]

can you move the "Filters" label to e.g.

updateDropdown('filters', ['Filters', ...stored_filters]); // if this works

Or is this not meant as label?

[gmt4]

There's a simpler solution I didn't know which is using a disabled option + title="Filters" so it shows 1) when no filter is selected, and 2) when on hover:

<select id="filterFiltersSelect" class="form-control form-select"  style="width:6em" title="Filter"> 
 <option value="" disabled selected>Filter</option>            
</select>                                                 

I've tried adding the above HTML to frontend/index.html, and removing the 'Filters' from the settings.php and checked it works as expected, I mean the "Filters" string is kept out of the list of applicable filters, and is just a presentation string in HTML that doesn't get into the JavaScript logic.

I'm rather new to PR reviews, if this suits, then feel free to make the edits.

[mbolli]

nice, thanks. I only have one thing that needs to be addressed. the rest can be done after the merge.

[mbolli]

great, thanks!