style.mdoc.5: maintenence

[concussious]

• description: increase consistency and visibility by s/file/manual page/
• examples: s/No Doing Something/Doing Something/ (am I wrong? is this an easter egg?)
• examples: remove depreciated .Li macro
• examples: remove extra newline (remove outermost display block) (these two fix the linter warnings, but they do change the recommendation)
• see also: link roff language reference for mandoc

@0mp

Thanks!