refactor pluralize/singularize inflection logics

[sio4]

What is being done in this PR?

• refactor the data structure and the logic for the singular/plural inflection
• improved test cases and test logic for the same target

What are the main choices made to get to this solution?

• the simple logic for the singular/plural inflection is not good enough for the current data size
• we need code comments for the organized data. without it, it cannot be maintainable
• we need a new data structure to handle exceptional data efficiently

What was discovered while working on it? (Optional)

• English is toooooooo hard

List the manual test cases you've covered before sending this PR:

• all previous test cases were preserved basically
• but for some words, I found the data is not correct or needs to be corrected with the trend

fixes #61

Note that:
This is not huge but a kind of big change since the logic, data structure, and actual data are changed at the same time in a single PR. However, I tried to keep it simple per each commit to make it easy to track the whole change direction.

[sio4]

Hi @paganotoni , Happy New Year!

I had a "hard" time with this PR to fix the internal structure of this package. There were basically two issues:

• English inflection for the plural is hard (at least for me, but I cannot fix it)
• Flect has been grown for years by many contributors, patching one by one, and it became hard to maintain.

My direction for this PR was to make Flect has some rules for adding inflection rules, hard-coded words and exceptions, and test cases with an organized structure.

Please take a look at this PR. FYI, I tried to make it simple to review by isolating each change and each rule update within a single commit.

I would like to release it as v1.0.0 when you review and I fix all review comments if any.
Thanks!

[sio4]

References:

• https://en.wiktionary.org/wiki/Category:English_nouns_with_common_ending_formations
• https://en.wiktionary.org/wiki/Category:English_irregular_plurals
• e.g. https://trends.google.com/trends/explore?date=today+5-y&geo=US&q="antennae","antennas"
• e.g. https://www.wordmom.com/nouns/that-end-with-ze

#!/bin/bash

end=$1

[ "$end" = "" ] && {
	echo "usage: $0 end"
	exit
}

curl https://www.wordmom.com/nouns/that-end-with-$end 2>/dev/null \
  |grep "[a-z]*$end</li" \
  |sed 's,<li [^>]*>,https://en.wiktionary.org/wiki/,g;s,</li>,#English\n,g' \
  |grep https

[paganotoni]

Hey @sio4! Thanks for taking care of this one. Happy new year. It looks good to me.