Now that nroam inserts a non read-only \n after the sections so that text can be
inserted after nroam sections at the end of the buffer, remove the extra
read-only \n so that org-capture can insert templates.

* nroam.el (nroam--handle-org-capture): Remove function and advice.
* nroam-unlinked.el (nroam-unlinked--insert-toggle-button): Do not insert a
read-only newline as it prevents org-capture from inserting the template as it
tries to delete empty lines at the end of the buffer.

* nroam-backlinks.el (nroam-backlinks--insert-heading):
* nroam-unlinked.el (nroam-unlinked--insert-heading): Add the
:noexport: tag to prevent exporting nroam sections. See docstring of
`org-export-exclude-tags'.

* nroam-backlinks.el (nroam-backlinks-section):
* nroam-unlinked.el (nroam-unlinked-section):
* nroam.el (nroam-setup-maybe):
(nroam-update):
(nroam--org-roam-file-p):
(nroam--update-maybe): Fix docstrings according to `checkdoc'.

* nroam-backlinks.el:
* nroam-unlinked.el:
* nroam-utils.el: Remove package headers.

* nroam-unlinked.el: New file.
* nroam.el: Setup unlinked references section.