tools: re-implement lint-md without unified-args

unified-args ignores settings in the preset, expecting them to be in remarkrc files or passed on the command line instead. Realizing that we always send the same configuration options via the command-line anyway, this removes unified-args. This means the preset settings are now respected and it removes nearly over 28000 lines of code in the resulting rollup file.

I wasn't sure I was going to want to keep rollup so I started re-implementing this without it, but ended up putting a minimal rollup back as it still saves about 90000 lines of code vs. checking in node_modules.