Design-plone-theme

-------------------

- Added publiccode.yml [nzambello]
- a11y: fixed contrast in alerts/messages, WCAG 2 AAA compliant [nzambello]
- Breadcrumbs styles are now less specific in order to allow breadcrumbs viewlet to be moved in another manager
[pnicolli]

------------------

- Add personal-information link in header viewlet when an user is logged.
[cekk]

------------------

- Removed target="_blank" from header banner links [nzambello]

------------------

- Added 'big' scale in allowed_sizes, used in leadimage viewlet [fdelia]
- Enhancing styles for default Plone search page [nzambello]

------------------

- Fixed svg mimetypes icons dimensions [nzambello]

------------------

- A11y: added `alt` attribute to `img` in tile collections where missing [nzambello]