i make a 2d movement mechanic packet and i dont know which category is it (2d, tools, essentials)
If in doubt: browse those categories and see what’s in there. 
2D is for graphics - sprites, textures and such.
Essentials is, well, essentials. Must haves. Very few assets go into that. Even fewer should be in that category. IMO this category should be removed or closed for publishers so it remains a Unity Technologies only category. Many non-Unity assets in there seem like someone put them in the wrong category. Like tutorial projects should really be in the Game Kits category because that’s what they are. And the rest belongs elsewhere in Tools.
There are only two Unity Technologies assets in “Essentials - Asset Packs”. None under “Beta Projects”. Three in “Certification” - again only Unity Technologies assets. Then there’s 54 in “Tutorial Projects” finally but again 18 of those are from Unity Technologies.
So yours goes into the most fitting category under Tools.