feat: Allow for masking of attributes

[billyvg]

Note: this is more of an RFC
Ideally this would allow users to be able to mask attributes of DOM nodes. An example of this is placeholder which can be a bit suspicious to our users when our default state is that everything is masked.

This currently adds a new API, maskAttributesFn: (key: string, value: string, el: HTMLElement) => string, that is used as a callback in transformAttribute. I prefer this API as it gives more flexibility for users (though it may need to pass the el node for most flexibility), but it is a bit inconsistent with maskTextFn and maskInputFn.

other options:

* Rename this to something else (open to ideas)

• Change this to pass value, and dom element (similar to MaskInputFn) to customize masking instead of decision maker of when to mask and introduce a simpler declarative API for what attributes to mask
  * ???

[changeset-bot]

🦋 Changeset detected

Latest commit: 7481949

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 8 packages

Name	Type
rrweb-snapshot	Patch
rrweb	Patch
rrdom	Patch
rrdom-nodejs	Patch
rrweb-player	Patch
@rrweb/types	Patch
@rrweb/web-extension	Patch
rrvideo	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[colingm]

Just wanted to say that it is awesome to see this, we were going to be bringing up attribute masking from Pendo pretty soon anyways 😅

So in your solution you opt for just always calling the maskAttributeFn instead of having another option that specifies a list of attributes to mask (that could take a wildcard or something) and then only call the function on those particular attributes. Would an option like that provide much performance benefit? I guess it means we would save calling to the function on elements that never even have the attribute in the first place.

Another thought would be if we don't want a list of attributes as an option would it instead be better to just call the maskAttributeFn once per element and then let the function decide to mask multiple attributes all at once?