SAM/BAM/CRAM readers don't support @CO header

[athos]

The SAM/BAM/CRAM specification has the @CO header for one-line comments. It's defined as below:

@CO: One-line text comment. Unordered multiple @CO lines are allowed. UTF-8 encoding may be
used.
https://github.com/samtools/hts-specs/blob/be74ef71f3fad34eb86af83bd66338d7d569af99/SAMv1.tex#L356

However, the current implementation of the SAM/BAM reader doesn't read the @CO header properly.

Repro

$ samtools view -h header_comment.sam
@SQ	SN:chr1	LN:1000	M5:258e88dcbd3cd44d8e7ab43f6ecb6af0
@CO	This is a comment.
@CO	This is also a comment.

(require '[cljam.io.sam :as sam])

(with-open [r (sam/reader "header_comment.sam")]
  (sam/read-header r))
;=>
{:SQ [{:SN "chr1", :LN 1000, :M5 "258e88dcbd3cd44d8e7ab43f6ecb6af0"}],
 :CO [{:This is a comment. nil} {:This is also a comment. nil}]}

Note that the comment contents themselves are read as keywords including whitespaces.