Convert issues templates from markdown to YAML

[vitormattos]

GitHub have a specific syntax for issues using forms:

https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/syntax-for-issue-forms

We have for now two templates in markdown that would be good to be converted to YAML:

https://github.com/LibreSign/libresign/tree/main/.github/ISSUE_TEMPLATE

to-do

• Verify examples at other repositories of Nextcloud apps and other kind of similar systems to get ideas to new form fields
• Check if have other forms that we can implement
• Convert bug report to yaml and use forms
• Convert feature request to yaml using forms