docs: introduce importing document

[jakovljevic-mladen]

Description:
As of RxJS version 7.2.0, a new way of importing operators is introduced. This PR adds a document that covers this addition.

Related issue (if exists):
None

[ladyleet]

@benlesh any comments on this one?
@niklas-wortmann i saw you looked this over a bit?

[benlesh]

@jakovljevic-mladen this is a very detailed document. I think one thing I would like to see if that directly at the top as bold as possible, we state very simply and plainly as possible that as of 7.2, no one should be importing things from rxjs/operators, and should import those things from rxjs instead.

Like, I wouldn't make people scroll or read too far at all before they saw that. It should be bold and obvious.

[jakovljevic-mladen]

@benlesh

we state very simply and plainly as possible that as of 7.2, no one should be importing things from 'rxjs/operators'

Got it, will add.

How about code examples in the docs? This isn't updated anywhere. I was thinking about adding some PRs to update this, but import from 'rxjs/operators' is still not officially deprecated and is also quite a new addition, so users using lower versions might have issues. Thus, I was thinking to refactor code examples; for example from this:

import { fromEvent } from 'rxjs';
import { filter } from 'rxjs/operators';

to this:

import { fromEvent, filter } from 'rxjs';
// If you're using RxJS v7.1 or lower, use this import
// import { fromEvent } from 'rxjs';
// import { filter } from 'rxjs/operators';

What do you think about doing it this way? Or I should just do this:

import { fromEvent, filter } from 'rxjs';

[benlesh]

How about code examples in the docs? This isn't updated anywhere.

Yeah. This needs updated everywhere.

[niklas-wortmann]

We do have the <span class="informal">CONTENT GOES HERE</span> that we use in several places to give a TLDR. I think that would be good to highlight that you don't need rxjs/operators anymore

[niklas-wortmann]

LGTM. Thanks for writing a document about this!

[niklas-wortmann]

I created a seperated ticket for updating the imports in the code example. I guess it would be the best to do this in a separate PR as it will be quite bloated probably.

[jakovljevic-mladen]

@benlesh @niklas-wortmann

Updated, it looks like this now:

It's not the first section in the document, but it's still visible without scrolling. Is this OK? And, yes, I used <span class="informal">, plus I used bold content.

@niklas-wortmann

I guess it would be the best to do this in a separate PR as it will be quite bloated probably.

I was thinking about doing it in separate PRs, not this one. Thanks for creating an issue for this.