left battery charging for three months

Hello. I bought the framework 13 inch and like a big dummy I left it with the charger in for three months. I chose the 'bring your own OS' and in the meantime I've been learning about linux with the goal of installing Gentoo, but that's besides the point.

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I didn't know this could damage the batter how much damage do you think I've done. I'm using the Framework brand charging block.