Feature: Add missing en language to i18n directories for plugins

[misilot]

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Current Behavior

For example the CAS Plugin: https://github.com/artefactual/atom/tree/qa/2.x/plugins/arCasPlugin/i18n does not have the default english language.

So we cannot update the textual strings used, for example "Log in with CAS"

Thanks!

Expected Behavior

Ability to update english language strings without having to generate the files from scratch.

Possible Solution

No response

Context and Notes

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Version used

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Operating System and version

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Default installation culture

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PHP version

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Contact details

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