docs: account for this context

[liamdebeasi]

Issue number: N/A

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What is the current behavior?

In #28694 there was some confusion around how to access this inside of a callback function passed to a property on Ionic components. The root issue was due to how the this context is determined with developers being responsible for setting the appropriate this context.

What is the new behavior?

• While this isn't an Ionic bug, I think it's worth calling out this behavior so developers are aware of how to account for it.

Does this introduce a breaking change?

• Yes
• No

Other information

Note: The link in the docs will not work until ionic-team/ionic-docs#3333 is merged.

[thetaPC]

Suggested change

	* Developers who wish to access "this" inside of the function
	* Angular developers who wish to access "this" inside of the function

Should it specify the framework? My concern is that other framework users might get confused with the comment.

[averyjohnston]

I question if this is the best way to document this tip, for a few reasons:

1. It creates a lot of duplicate text, which is annoying to maintain.
2. I can see us easily forgetting to add the same tip to any future function props.
3. It seems to be Angular-specific -- I was unable to access the right this in React (using an arrow function) or Vue (using .bind(this)). If it does actually apply to React or Vue, but my example is just subtly wrong, that only speaks to the need for example code somewhere.

Maybe we could put it in Development Tips instead? Or a page in the Angular-specific docs if it really is only relevant to Angular? I know that's not as discoverable, but my understanding is that this isn't an Ionic-specific issue, so I'm unsure if we need to give it much priority in the docs.

[thetaPC]

LGTM

[averyjohnston]

LGTM aside from a component that was missed when updating to the link.