Regular expression for valid AS numbers doesn't allow for AS 0
https://metrics.torproject.org/rs.html#aggregate/as
links to
https://metrics.torproject.org/rs.html#search/as:AS0
results in
https://onionoo.torproject.org/details?search=as:AS0
returns:
```
HTTP ERROR 400
Problem accessing /details. Reason:
Bad Request
```
issue