Convert manual from Wiki to mld

This allows to view the manual offline. Converted with:

    sed -E \
        -e 's/^==== *(.*) *====/{3 \1}/g' \
        -e 's/^=== *(.*) *===/{2 \1}/g' \
        -e 's/^== *(.*) *==/{1 \1}/g' \
        -e 's/^= *(.*) *=/{0 \1}/g' \
        -e 's/\[\[(.*)\|(.*)]]/{{: \1 }\2}/g' \
        -e 's|//(.*)//|{e \1}|g' \
        -e 's/<<a_api text=".*" *\| module (.+)>>/in {!\1}/g' \
        -e 's/<<code language="ocaml" *\|/{[\n/g' \
        -e 's/<<code language="c" *\|/{@c[/g' \
        -e 's/>>/]}/g' \
        -e "s/\`\`(.*)''/“\1”/g" \
        -e 's/\.\.\./…/g' \
        "$@" | \
        perl -pe 's|{{{(.*?)}}}|[\1]|g'

and then some manual fixes for lists and tables.

docs/dune

@@ -0,0 +1,3 @@
+(documentation
+ (package lwt)
+  (mld_files :standard))