[DOC] Doc for StringIO#putc (#196) #635

Job	Run time
ruby-versions / Generate Ruby versions	4s
ubuntu-24.04 3.0	17s
ubuntu-24.04 head	14s
ubuntu-22.04 3.2	18s
ubuntu-24.04 3.4	17s
ubuntu-24.04 truffleruby-head	32s
ubuntu-22.04 3.1	17s
ubuntu-22.04 3.3	14s
ubuntu-22.04 2.7	51s
ubuntu-24.04 2.7	43s
ubuntu-24.04 debug	24s
ubuntu-22.04 3.0	13s
ubuntu-24.04 3.2	21s
ubuntu-24.04 jruby-head	1m 3s
ubuntu-22.04 jruby-head	7m 31s
ubuntu-22.04 head	18s
ubuntu-22.04 debug	24s
ubuntu-24.04 3.3	17s
ubuntu-22.04 truffleruby-head	39s
ubuntu-24.04 3.1	17s
ubuntu-22.04 3.4	17s
	15m 31s

Provide feedback