Create a new importer for tailscale

[Rafiot]

Source: https://tailscale.com/security-bulletins/index.xml

[Rafiot]

Few notes on this feed:

• RSSv2, not in any specific vulnerability reporting format
• The publication date is the date of the entry in the RSS feed, not sure what happens if there is an update (pubDate)
• No easy way to get a CVE reference (besides regex against the description for some entries)
• The feed is re-generated every minute or so, regardless if an entry is added or not (lastBuildDate)
• The description is in HTML, so we need to either display as-is, or strip the HTML tags.
• The HTML contains relative URLs -> converted appropriately by feedparser

[Rafiot]

Fixed by: https://github.com/cve-search/vulnerability-lookup/commit/1206331b5f61df06b09d0181c27d97ce5293a25e