fix: invoke callback after after-highlight hook

[Jocs]

Hi, first thanks for you for provide so cool library.

when I use prism.highlightElement with keep markup plugin. I have encountered some problems.

 const code = '<span class="highlight">const a = "nice"</span>'
 const lang = 'javascript'
 const wrapper = document.createElement('div')
 wrapper.classList.add(`language-${lang}`)
 wrapper.innerHTML = code
 prism.highlightElement(wrapper, false, function () {
    const highlightedCode = this.innerHTML
})

expect highlightedCode contains with span.highlight markup, but it does not. because the callback called before after-highlight hook?

[RunDevelopment]

callback according to the documentation:

An optional callback to be invoked after the highlighting is done. [...]

Now, when exactly do we consider that "highlighting is done"? Right now that is after the highlighted code is inserted into its element.

Wouldn't it be better if the callback were invoked after the complete hook was run so that all plugins (including line numbers and command line) take effect?

---

Also, callback is invoked in line 252 and line 270 so we have to change both.

[Jocs]

Wouldn't it be better if the callback were invoked after the complete hook?

Yeh, I think it's better, I'll update this PR.

[Jocs]

@RunDevelopment Updated this PR, can you help review it?

[RunDevelopment]

@Jocs Well, I can do that but please run gulp before.

[Jocs]

@RunDevelopment I have run gulp and build the min file. 😸

[RunDevelopment]

I looked at the code and everything seems to be allright. The Prism website works as expected.

@mAAdhaTTah What do you think about this change?

[mAAdhaTTah]

Intuitively, this feels "right", in that highlighting isn't "done" until after everything has run. I guess I'm a little concerned this could be a breaking change for anyone relying on callback to be run before those hooks.

[Jocs]

@mAAdhaTTah I think we can give a notification in the changelog. After all, according to the documentation, the callback should be placed after after-highlight, and I really need such a callback.

[mAAdhaTTah]

Merged as a bugfix.

[Jocs]

@mAAdhaTTah �BTW, when will release this bugfix version?

[mAAdhaTTah]

I'm not sure, tbh. Admittedly, we tend to release infrequently because you can always download the latest from the website.

[Jocs]

@mAAdhaTTah thank you!