Editorial notes (incremental)

Carrying on the tradition of #2408: * [ ] `FODC0013`: Raised when the the options * [ ] To be removed: “map:get raises a type error when applied to a record if the requested key does not match any field name defined for the corresponding record type.” * [ ] To be removed: “map:put, when applied to a record, returns an instance of the same record type, and therefore raises a type error if either the supplied key or the supplied value is not valid for that record type.” * [ ] `map:filter(fn($k, $v){ exists($v) }) => map:size()`<br>→ `map:filter($map, fn($k, $v) { exists($v) }) => map:size()` or<br>→ `$map => map:filter(fn($k, $v) { exists($v) }) => map:size()` To keep the list short, I will incrementally edit my existing comments until the next PR is finalized.