Positive numbers with plus sign not quoted correctly with `ALWAYS_QUOTE_NUMBERS_AS_STRINGS`

[dyadyaJora]

Hello!
I found a case which is very similar to #182 but for positive numbers with plus sign.
Serializing 14 currently results in "14".
Serializing -14 currently results in "-14".
But Serializing +14 currently results in +14, instead of "+14".

It looks like update PLAIN_NUMBER_P regexp with (-|\\+)?[0-9]*(\\.[0-9]*)? in https://github.com/FasterXML/jackson-dataformats-text/blob/2.15/yaml/src/main/java/com/fasterxml/jackson/dataformat/yaml/YAMLGenerator.java#L220 should solve this problem.
https://regex101.com/r/eQo6ag/1

Do you have any objections about this fix?
I am ready to open PR =)

[yawkat]

im not sure this is a good idea. numbers can get much more complicated than that pattern (octal, exponent, ...), so i'm not sure why a preceding + should be allowed but more complicated patterns should not be.

[cowtowncoder]

While I agree there may be complications wrt more complex numbers, I do think that addressing this particular issue still makes sense. So I'd be +1 for a patch -- if so, against 2.15 as its still behavioral change that could cause some (bogus test?) failures somewhere and it's better to keep those to minor versions.

[cowtowncoder]

Implemented as suggested; only adds support for leading +, no further changes for octals etc (not against those but solving one issue at a time, lowest hanging fruit)