v2.5.0 - Working selfupdater & instance JSON builder

What's Changed

• Much improved instance.json builder by @neil-morrison44 in #75

• Accessed from the Instance JSON button within the Games section

• Now cores can be distributed with an instance-packager.json file which tells updaters (etc) how to find the files needed by the core & package them into instance.json files

• There's a standalone binary available on https://github.com/neil-morrison44/openfpga-instance-packager & a readme with the file's specification ( a collaborative effort between myself, @mattpannella, & @Mazamars312 )

• The format's probably very useful for future consoles - e.g. the NeoGeo core, for example, wouldn't need to be distributed with all the json files regardless of if the user has those games installed anymore.

• Less useful for Arcade cores though since the expectation is the user won't have the arcade files already & the instance json files are what tells the updaters which files to look for

• Also the App's self update should work across all platforms now so you might not even be reading this

Full Changelog: v2.4.0...v2.5.0

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