fix(tech/home): use image_tag for fork.png so /tech/ prefix is honored
../images/fork.png is a relative path that resolves to /images/fork.png
from /tech/index.html. On github.io that accidentally hit utensil.github.io's
user-page /images/fork.png; on tngl.sh there's no parent user page, so it
404'd. image_tag respects http_prefix=/tech/ and emits /tech/images/fork.png.