When you have any full set of armor with the exclusion of leather and chainmail particles will spawn around you
So in a more formal form here are all the armors that work with it
Iron armor
Gold armor
Diamond armor
Netherite armor
And the armor types that don't
Leather armor
Chainmail armor
Turtle shellmet
All modded armors
Note that the procedure used is called every tick so it may cause some slight lag on some computers
Added shine particle
Added procedure for spawning particle when full sets of iron, gold, diamond, or netherite armor is equipped
Added shining enchantment
Particles now require the shining enchantment to spawn
Cool mod, in order to make it more universal, you should create a tag, maybe "#forge:shiny_armors" and use that instead of manually setting the types of armor. this would allow mod devs to tag their armors so that, if this mod is installed, their modded armor will shine.
Could you make it an enchantment?