Implementation of Booleans handler like pluralization

[robinsondotnet]

This PR is related to the following issue: #722

[codecov-io]

Codecov Report

Merging #767 into v8.x will increase coverage by 0.03%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##             v8.x    #767      +/-   ##
=========================================
+ Coverage   96.26%   96.3%   +0.03%     
=========================================
  Files          10      10              
  Lines         803     811       +8     
=========================================
+ Hits          773     781       +8     
  Misses         30      30

Impacted Files	Coverage Δ
src/extend.js	100% <100%> (ø)	⬆️
src/index.js	97.84% <100%> (+0.02%)	⬆️

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[kazupon]

@robinsondotnet
Thank you for your PR!
Could you write the docs, please?

[Soviut]

@robinsondotnet would you like me to write the documentation for this so that it can be merged?

[robinsondotnet]

@robinsondotnet would you like me to write the documentation for this so that it can be merged?

@Soviut Sure. Thanks.

[DutchGerman]

What is the status on this PR? Is the documentation already written, could I help here?

[Soviut]

@DutchGerman I'm sorry, I don't think I ever received the notification for this back in August. I'll have to refamiliarize myself but I do want this to get merged.

[Soviut]

@robinsondotnet I've been working on the docs but will need to collaborate with you to contribute them to this PR. I've never had to contribute to a 3rd party PR before so I'm not sure if I need to be invited as a contributor to it or something?

@kazupon I've got most of the English documentation done, but I'm wondering what I need to do about the zh pages. For example, I've created a new /guide/boolean.md page, should I duplicate it in the /zh/guide directory and leave it as English until someone can translate it?

[robinsondotnet]

@Soviut Thanks! I have invited you as collaborator to robinsondotnet/vue-i18n in order to give you access to the branch is selected in this PR.

[vincenzomartusciello]

no eta to know when it will be merged?

[Soviut]

@robinsondotnet I fixed the merge conflict in the tests. This could be merged.

[Soviut]

@kazupon I'm not sure who I should be asking for final review and merge on this, so I'm pinging you.

[wolfgangwalther]

The last PR to be merged in this repo was in 2022, so don't expect too much.

[BobbieGoede]

Continued development on vue-i18n is on this repo https://github.com/intlify/vue-i18n, but it targets Vue 3