Add destroyDelay prop

[doutatsu]

Fixes #579

The original issue was marked as completed, but it was not fixed. To address this issue, I've added a new prop that delays calling destroy on unMount. No matter how long your transition is, you can adjust the charts as a result

Before

chart-bug.mp4

With delay

graph-fixed.mp4

[apertureless]

Hey! Thanks for the PR. Honestly I thought this was fixed a while ago.
Reading the initial issue, as far as I understand the problem is, that if you are using vue-router and have transitions for the page changes, the charts get destroyed too early.

It would be good to have a reproduction for this. However, I do not think that adding a setTimeout is the proper way here.

I think it would be easier and cleaner to destroy the chart on the onUnmounted hook instead of onBeforeUnmount https://github.com/doutatsu/vue-chartjs/blob/allow-destroy-delay/src/chart.ts#L70

But this needs some testing if it is really solving the issue.

[doutatsu]

@apertureless That's a good point, thank you for a quick response. I'll see if simply using a different lifecycle hook will do the trick and if so, update this PR to reflect the changes

[doutatsu]

@apertureless It doesn't seem to do the trick unfortunately - it still gets destroyed too quickly, unlike when I use a simple delay. I've added videos to demonstrate the problem and fix

[doutatsu]

@apertureless Any updates on this?