Add tags (primary/related) to links

This change allows more complex scope boundaries, including loosening
edges a bit to include related resources of HTML pages (which makes
for more complete archives if desired).
1 job for master in 15 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
failed #2343
run_tests

00:00:15

 
Name Stage Failure
failed
run_tests Test There is an unknown failure, please try again
=== RUN   TestSchemeScope
--- PASS: TestSchemeScope (0.00s)
=== RUN TestURLPrefixScope
--- PASS: TestURLPrefixScope (0.00s)
PASS
ok git.autistici.org/ale/crawl 6.048s
? git.autistici.org/ale/crawl/analysis [no test files]
? git.autistici.org/ale/crawl/cmd/crawl [no test files]
ERROR: Job failed: exit code 1