Accessibility issues 2/2

According to the feedback from Statistics Finland accessibility review

Catalogue tree:

- [x] The category names are all level 3 headings, probably they wouldn't need to be headings and if they are, they should be hierarchical #3336
- [x] #3336
- Note: catalogue tree seems to be implemented as HTML table, actually it seems to be some kind of a drop down menu. When using a screenreader this causes it to start reading out rows and colums. #3352

Application

- [ ] The pdf export is not accessible, low priority
- #3335
- [ ] Search box and form field border contrast is too light
- [ ] Applicant information fields look like they can be edited even though they cannot (this is low priority)

Other:

- [ ] Skip to main content works a bit illogically: The whole content has been set as main content which is why the screen reader might read through the whole page when navigating with the link. Also the link seems to work only on the first time and quit working after that. Could it be a browser issue?
- [ ] Fixes to aria-label texts: in language selection vaihda kieleksi EN is not descriptive enough. "Olisi parempi olla ohjeteksti englanniksi ja sille lang-merkintä en."
- [ ] the language selection EN FI SV should be added to extra-translations so we can modify it to be more descriptive (suomi, english, svenska)
- [ ] There are some warnings in code: "Normaalilla koodinäkymällä (ctrl+u) löytyi yksi ongelma, tupla-html-tagi. Inspektorilla tutkimalla ei virheitä, vain varoituksia. Katalogisivulla sama tilanne. Hakemussivulla 81 virhettä ja varoitusta, tässä korjattavaa."

First issue: #2430