feat(): fire contextmenu event

[ShaMan123]

fire contextmenu:before, contextmenu
these are useful for devs

[github-actions]

Code Coverage Summary

> fabric@5.1.0 coverage:report
> nyc report --reporter=lcov --reporter=text

-----------|---------|----------|---------|---------|-----------------------------------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s                             
-----------|---------|----------|---------|---------|-----------------------------------------------
All files  |   83.32 |    76.76 |   86.53 |   83.05 |                                               
 fabric.js |   83.32 |    76.76 |   86.53 |   83.05 | ...,29681,29806,29886-29951,30074,30173,30390 
-----------|---------|----------|---------|---------|-----------------------------------------------

[github-actions]

Code Coverage Summary

> fabric@5.1.0 coverage:report
> nyc report --reporter=lcov --reporter=text

-----------|---------|----------|---------|---------|-----------------------------------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s                             
-----------|---------|----------|---------|---------|-----------------------------------------------
All files  |   83.32 |    76.76 |   86.53 |   83.05 |                                               
 fabric.js |   83.32 |    76.76 |   86.53 |   83.05 | ...,29681,29806,29886-29951,30074,30173,30390 
-----------|---------|----------|---------|---------|-----------------------------------------------

[github-actions]

Code Coverage Summary

> fabric@5.1.0 coverage:report
> nyc report --reporter=lcov --reporter=text

-----------|---------|----------|---------|---------|-----------------------------------------------
File       | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s                             
-----------|---------|----------|---------|---------|-----------------------------------------------
All files  |   83.27 |    76.72 |   86.53 |   82.99 |                                               
 fabric.js |   83.27 |    76.72 |   86.53 |   82.99 | ...,29681,29806,29886-29951,30074,30173,30390 
-----------|---------|----------|---------|---------|-----------------------------------------------

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[asturur]

I m ok with this, but at the next occasion update the fires section of the canvas documentation. (@fires contenxtMenu... ) Try to make the example of why you need both in the docs ( i m sure using prevent default in the native event does not stops firing contextMenu, so i don't see the reason for contextmenu:before )

[ShaMan123]

The reason is that canvas is fired with the event first but what if you want the target to handle the event.
Then the before event is useful.