We use the following site for that now:

* https://tools.ietf.org/ or http
* https://datatracker.ietf.org or http

Today, IETF said the official site of RFC is www.rfc-editor.org.

FYI: https://authors.ietf.org/en/references-in-rfcxml

I replaced them to www.rfc-editor.org.

(https://github.com/ruby/csv/pull/276)

I've fixed the example in `Recipe: Capture Unconverted Fields`.

https://ruby.github.io/csv/doc/csv/recipes/parsing_rdoc.html#label-Recipe-3A+Capture+Unconverted+Fields

`parsed` is wrong: header row is missing and the values should be
integers.

```
$ ruby -v
ruby 3.2.1 (2023-02-08 revision https://github.com/ruby/csv/commit/31819e82c8) [x86_64-darwin21]

$ cat unconverted_fields.rb
require "csv"

source = "Name,Value\nfoo,0\nbar,1\nbaz,2\n"
parsed = CSV.parse(source, converters: :integer, unconverted_fields: true)
p parsed
parsed.each {|row| p row.unconverted_fields }

$ ruby unconverted_fields.rb
[["Name", "Value"], ["foo", 0], ["bar", 1], ["baz", 2]]
["Name", "Value"]
["foo", "0"]
["bar", "1"]
["baz", "2"]
```

https://github.com/ruby/csv/commit/d5e401266f

(https://github.com/ruby/csv/pull/190)

https://github.com/ruby/csv/commit/2102c78384

https://github.com/ruby/csv/commit/77ccf486fe

https://github.com/ruby/csv/commit/5adeaff91f

https://github.com/ruby/csv/commit/d9e67918e2

https://github.com/ruby/csv/commit/bee48b04c4

Co-authored-by: Sutou Kouhei <kou@clear-code.com>

https://github.com/ruby/csv/commit/f0bab6a592