textproc/write-good: Add a new port

write-good is a naive linter for English prose. For example,
it is able to check for the following issues in text:

• passive voice
• lexical illusions – cases where a word is repeated
• "so" at the beginning of the sentence
• "there is" or "there are" at the beginning of the sentence
• weasel words
• adverbs that can weaken meaning: really, very, extremely, etc.
• wordy phrases and unnecessary words
• common cliches

WWW: https://github.com/btford/write-good

Requested by: bcr (via https://wiki.freebsd.org/WantedPorts)