Add a missing note about plugin webapp utility function (PostUtils.formatText)

[kaakaa]

Summary

When replacing ~channel mention with a link by PostUtils.formatText, just specifying channelNamesMap as args didn't get a correct result, and it was required to specify team arg at the same time. The document doesn't mention this, so it should be added.

Ticket Link

N/A

Additional Context

...
    // msg1: no options
    const msg1 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {}
    ), true, {});
    // msg2: just `channelNamesMap`
    const msg2 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {channelNamesMap}
    ), true, {});
    // msg3: `channelNamesMap` and `team`
    const msg3 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {channelNamesMap, team}
    ), true, {});
...

Entire code

import React from 'react';

import {getChannelsNameMapInCurrentTeam} from 'mattermost-redux/selectors/entities/channels';
import {getCurrentTeam} from 'mattermost-redux/selectors/entities/teams';
import { useSelector } from 'react-redux';

const {formatText, messageHtmlToComponent} = window.PostUtils;

const Sub = () => {
    const channelNamesMap = useSelector((state) => getChannelsNameMapInCurrentTeam(state));
    const team = useSelector((state) => getCurrentTeam(state));

    // msg1: no options
    const msg1 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {}
    ), true, {});
    // msg2: just `channelNamesMap`
    const msg2 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {channelNamesMap}
    ), true, {});
    // msg3: `channelNamesMap` and `team`
    const msg3 = messageHtmlToComponent(
        formatText(`link: ~off-topic`, {channelNamesMap, team}
    ), true, {});

    return (
        <div>
            <h3>msg1</h3>
            <div>{msg1}</div>
            <h3>msg2</h3>
            <div>{msg2}</div>
            <h3>msg3</h3>
            <div>{msg3}</div>
        </div>
    );
}

export default Sub;

---

Without team, replacing token isn't seemed to be fired.
https://github.com/mattermost/mattermost/blob/f111db5fe85e8320fbc4b88b75cd423e181a7600/webapp/channels/src/utils/text_formatting.tsx#L546

[mattermost-build]

Hello @kaakaa,

Thanks for your pull request! A Core Committer will review your pull request soon. For code contributions, you can learn more about the review process here.

[hmhealey]

Thanks for the PR! That's a great catch. From what I can tell, team has been required for channel short links for a while now, so it's good to have that fixed

[cwarnermm]

Thank you for this great developer documentation PR, @kaakaa!

[github-actions]

Newest code from cwarnermm has been published to preview environment for Git SHA 56458ab

[github-actions]

Newest code from cwarnermm has been published to preview environment for Git SHA b8dcfd6