vyos - add v1.3.0-epa1

[b-ehlers]

VyOS published another publicly available pre-release of v1.3.0: v1.3.0-epa1, epa means “early production access”.

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Before submitting a pull request, please check the following.

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When updating an existing appliance:

• [x] The new version is on top.
• [x] The filenames in the "images" section are unique, to avoid appliances / version overwriting each other.
• [x] If you forked the repo, running check.py doesn't drop any errors for the updated file.