feat(providers): add Nextcloud provider (#11837)
* added nextcloud provider with logo and styles
* added docs
* added nextcloud to issue template
* style update
* remove dark mode
* fix bug reading issuer
* clean up
* update documentation
* Update nextcloud.ts
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Co-authored-by: Nonthaphat Chaisu <48936015+Podter@users.noreply.github.com>
Co-authored-by: Balázs Orbán <info@balazsorban.com>
