Support encoding of comment node

[goccy]

Supports comment encoding.
This allows you to parse the following document with comments and undo it !

# foo comment
# foo comment2
foo: # map key comment
  # bar above comment
  # bar above comment2
  bar: 10 # comment for bar
  # baz above comment
  # baz above comment2
  baz: bbbb # comment for baz
  piyo: # sequence key comment
  # sequence1 above comment 1
  # sequence1 above comment 2
  - sequence1 # sequence1
  # sequence2 above comment 1
  # sequence2 above comment 2
  - sequence2 # sequence2
  # sequence3 above comment 1
  # sequence3 above comment 2
  - false # sequence3
# foo2 comment
# foo2 comment2
foo2: &anchor text # anchor comment
# foo3 comment
# foo3 comment2
foo3: *anchor # alias comment

f, err := parser.ParseBytes([]byte(yml), parser.ParseComments)
if err != nil {
  panic(err)
}
fmt.Println(f.String()) // You can get the same as the original document