Fix malformed uri

[manunio]

While Fuzzing locally using jazzer.js YAML.parse() threw uncaught exception at

yaml/src/doc/directives.ts

Line 149 in a4d8569

if (prefix) return prefix + decodeURIComponent(suffix)

this pr attempts to fix that.

URIError: URI malformed
    at decodeURIComponent (<anonymous>)
    at Directives.tagName (/home/maxx/dev/security/oss-fuzz-projects/eemeli-yaml/dist/doc/directives.js:126:29)

[eemeli]

Thank you for reporting this! In general the fix looks right, but see line comments for details.

[eemeli]

Looks good! I realised that there's a better place for the test, so I moved it there.