Support proposals dmitri.shuralyov.com/website/gido#6

It would be great if the "proposal: " prefix were supported.

Proposals are already supported, in the sense they're listed as issues at https://goissues.org/ with a "Proposal" label.

See prefixtitle.ParseIssue documentation:

Supported forms include:

"",    "import/path: issue title"    -> ["import/path"],            "issue title"
"",    "proposal: path: issue title" -> ["path"],                   "issue title"  # Proposal.
"",    "Proposal: path: issue title" -> ["path"],                   "issue title"  # Proposal.
[...]

Or do you mean something else?