[OMP] Add funding data to ONIX export

[kaitlinnewson]

When an OMP user has installed and enabled the funding plugin from the plugin gallery, that metadata should be included in the ONIX export when populated.

Sample for funder data from ONIX documentation p.4:

<Publisher>
    <PublishingRole>16</PublishingRole> <!-- funding body -->
    <PublisherIdentifier>
        <PublisherIDType>40</PublisherIDType> <!-- ROR -->
        <IDValue>029chgv08</IDValue>
    </PublisherIdentifier>
    <PublisherIdentifier>
        <PublisherIDType>32</PublisherIDType> <!-- FundRef DOI -->
        <IDValue>10.13039/100010269</IDValue>
    </PublisherIdentifier>
    <PublisherName>Wellcome Trust</PublisherName>
    <Funding>
        <FundingIdentifier>
            <FundingIDType>01</FundingIDType> <!-- proprietary -->
            <IDTypeName>Wellcome Grant No</IDTypeName>
            <IDValue>2018/701a</IDValue>
        </FundingIdentifier>
    </Funding>
</Publisher>

What application are you using?
OMP 3.3/3.4/main

Additional information
Tagging @ajnyga to add any relevant notes about the plugin and/or the plugin metadata.

[asmecher]

Here's an example of the Publication Facts Label plugin making use of funding plugin data, when that plugin is installed and available. Not a great example to promote, as it leads to cross-dependencies, but anyway: https://github.com/asmecher/pflPlugin/blob/3b84f0daff1b5291d6c7213458783ea87228c239/PflPlugin.inc.php#L177..L192

[ajnyga]

And the second option is to do this from the Funding plugin side if there is a hook to be used https://github.com/ajnyga/funding/blob/master/FundingPlugin.inc.php#L79-L81