Put it in "C:\Users\{Your-Name}\AppData\Roaming\GIMP\2.10\plug-ins" instead!!
Restart and it should appear at Filters/Decor/Text Outline
EDIT: However, this plug-in seems to only work properly in GIMP 2.8 (just checked), they may be a
similar plug-in for 2.10 elsewhere not sure. Although the effect you're after is pretty straightforward to produce without extra scripts, check this video as an example (there may be better ones out there but this gives you the basic idea) - https://www.youtube.com/watch?v=Kdq6F8natcw
Restart and it should appear at Filters/Decor/Text Outline
EDIT: However, this plug-in seems to only work properly in GIMP 2.8 (just checked), they may be a
similar plug-in for 2.10 elsewhere not sure. Although the effect you're after is pretty straightforward to produce without extra scripts, check this video as an example (there may be better ones out there but this gives you the basic idea) - https://www.youtube.com/watch?v=Kdq6F8natcw