New Slack and wording improvements in templates

NetBox should always be referred to as NetBox ...

Fix all instances of "Netbox".

```Shell
git ls-files -z . | xargs --null -I '{}' find './{}' -type f -print0 | xargs --null sed --in-place --regexp-extended 's#Netbox#NetBox#g;'
```

Ref: https://netbox.readthedocs.io/en/stable/development/style-guide/#branding

Change the phrasing of the alternative options

Create config.yml for ISSUE_TEMPLATE ...

This commit adds links to the _New Issue_ section of Github.
The intention is to provide more hints where to get help and
further reduce the amount of Github issues that can not be
acted upon.