a fix to indentation related to comma syntax

[tiye]

Normally we can write:

a b c d e

with comma syntax, since the essence of comma syntax actually increase a level of indentation, it could become

a
 , b c d e

then again, it could be:

a
  , b
  , c d e

or also(counter-intuitively):

a
  , b
    , c d e

and even:

a
  , b
    , c
      , d
        , e

while it still parses to:

[["a" "b" "c" "d" "e"]]

so I have to increase internal indentation level of followed siblings.

Optimal solution would be detecting the span of token after "comma syntax" and turn level followed expressions back to normal indentation level. I'm not able to do that at current based this codebase.