fix(build) Remove source map from build distribution

[jeromesimeon]

Signed-off-by: Jerome Simeon jeromesimeon@me.com

Issue #142

Trying to address the issue raised in #142 wrt to test coverage in applications importing markdown-transform.

Changes

• Distinct babel configuration for production build, which does not include Istanbul.
• Use production build when publishing the packages

Flags

• I do not understand jest testing very well, I only replicated the fix that occurred in Cicero related to the same issue. I am not sure how to test it either, so could use help with that or a review from someone who understands this better, possibly from @mttrbrts or the issue's originator (@j4m3sb0mb)