feat: add support for LightningMessageChannel

[froucher]

Adding support to meta_lightningmessagechannel, it is in Beta, but I need to add it.

The metadata reference link is: https://developer.salesforce.com/docs/atlas.en-us.api_meta.meta/api_meta/meta_lightningmessagechannel.htm

Sample:

src/messageChannels/sample.messageChannel

<?xml version="1.0" encoding="UTF-8"?>
<LightningMessageChannel xmlns="http://soap.sforce.com/2006/04/metadata">
    <description>Lightning Message Channel Sample</description>
    <isExposed>true</isExposed>
    <lightningMessageFields>
        <description>Field Sample 1</description>
        <fieldName>recordId</fieldName>
    </lightningMessageFields>
    <lightningMessageFields>
        <description>Field Sample 2</description>
        <fieldName>debtorName</fieldName>
    </lightningMessageFields>
    <masterLabel>sample</masterLabel>
</LightningMessageChannel>

This resolves #223

[amtrack]

@froucher Looks good to me so far!

I don't have any experience with this metadata type yet. It doesn't have a -meta.xml file (like ApexClasses), right?

[froucher]

No, it doesn't have 'meta' file.

Thanks!

[amtrack]

:tada: This PR is included in version 2.6.0 :tada:

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot :package::rocket:

[froucher]

Thank you!! 👏 👏 👍