[Search page] Add search input and filters

[tkohr]

This PR adds the search form to the search page and a load more button at the bottom of the page.

The search input has not been adapted to the design yet, as the search input from #23 will be reused for this.

Todos:

• integrate mel search input from Search area homepage #23
• add e2e tests

[cmoinier]

Thanks for this big work! 👍

A few comments and behavior issues I noticed :

1. In some cases, if i type only a part of a word that I know will match (eg : "carto" or "conven") in the home page, it goes to the search page alright, but returns no results (when it should). When I do that with some other words (eg : 'alpen'), it returns the right results.

2. Shouldn't filter's numbers be updated with the search? for instance this is misleading for the user IMO (5 results but multiple themes have a count in the filters). I don't know if it's something that's done in gn-ui actually.
   

3. @Angi-Kinas if you test, FYI, you'll need to run npm install first to upgrade gn-ui deps.

[Angi-Kinas]

Thanks @tkohr this works like a charm :)

I noticed only a really small detail in the UI:

• the borders of the filter buttons are not rounded in the design, but it's almost not noticeable ;-)

[Angi-Kinas]

Thanks for cleaning this up! I don't know why I implemented it with overrides...

[tkohr]

Thanks for the detailed reviews @cmoinier @Angi-Kinas ! I've added a commit to address the rounded buttons and the tests.

Thanks also for pointing out the following two points:

1. In some cases, if i type only a part of a word that I know will match (eg : "carto" or "conven") in the home page, it goes to the search page alright, but returns no results (when it should). When I do that with some other words (eg : 'alpen'), it returns the right results.

2. Shouldn't filter's numbers be updated with the search? for instance this is misleading for the user IMO (5 results but multiple themes have a count in the filters). I don't know if it's something that's done in gn-ui actually.

I totally agree that both behaviors are not ideal, but they are identical in gn-ui. 1. seems to be due to search on entire words only. Not sure if there are bugs or if this has not been implemented yet, but it should be fixed or evolved in gn-ui.

[Angi-Kinas]

Thanks @tkohr for addressing the comments. I had another look and for me it looks good to go 🚀

[tkohr]

Just a note from the gn-ui daily regarding the two behaviors mentioned above:

1. The search currently does not execute a fuzzy search, but you can use a wildcard (like "carto*") to search for parts of a word
2. Improving the proposed options in the multiselect-dropdowns is a feature waiting for financing