Add mld6 source file to fix missing include (#214)

* clean up

* Add mld6 source file with include fix

* Restyle Add mld6 source file to fix missing include (#215)

* Restyled by whitespace

* Restyled by clang-format

* Restyled by prettier-markdown

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Co-authored-by: Restyled.io <[email protected]>

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Co-authored-by: restyled-io[bot] <32688539+restyled-io[bot]@users.noreply.github.com>
Co-authored-by: Restyled.io <[email protected]>