GitHub: fix GH-225

With Ruby 3.0.2 and csv 3.2.1, the file

```ruby
require "csv"
File.open("example.tsv", "w") { |f| f.puts("foo\t\tbar") }
CSV.read("example.tsv", col_sep: "\t", strip: true)
```

produces the error

```
lib/csv/parser.rb:935:in `parse_quotable_robust': TODO: Meaningful
message in line 1. (CSV::MalformedCSVError)
```

However, the CSV in this example is not malformed; instead, ambiguous
options were provided to the parser. It is not obvious (to me) whether
the string should be parsed as

- `["foo\t\tbar"]`,
- `["foo", "bar"]`,
- `["foo", "", "bar"]`, or
- `["foo", nil, "bar"]`.

This commit adds code that raises an exception when this situation is
encountered. Specifically, it checks if the column separator either ends
with or starts with the characters that would be stripped away.

This commit also adds unit tests and updates the documentation.

https://github.com/ruby/csv/commit/cc317dd42d

https://github.com/ruby/csv/commit/a802690e11

The implementation of the `CSV` shortcut method is broken in Ruby 3
for calls that look like this:

```ruby
CSV(write_stream, col_sep: "|", headers: headers, write_headers: true) do |csv|
  ...
end
```

The above will result in the following error when the `CSV` method attempts to pass
on arguments to `CSV#instance`:

```
ArgumentError: wrong number of arguments (given 2, expected 0..1)
```

The issue is due to the changes in Ruby 3 relating to positional & keyword arguments.

This commit updates the `CSV()` shortcut implementation to work with Ruby 3, and also
updates the documentation for the shortcut method.

https://github.com/ruby/csv/commit/310dee45fa

https://github.com/ruby/csv/commit/1f9cbc170e

It's for Ractor. If you want to use the built-in converters, you
should call Ractor.make_shareable(CSV::Converters) and/or
Ractor.make_shareable(CSV::HeaderConverters).

https://github.com/ruby/csv/commit/b0b1325d6b

https://github.com/ruby/csv/commit/744e41130c

https://github.com/ruby/csv/commit/117bcf311e

https://github.com/ruby/csv/commit/f3e9586b34

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

https://github.com/ruby/csv/commit/203c5e0574