readme: fix import path

[miku]

Originally, I got the following error message:

$ go get -u github.com/Anush008/fastembed-go
go: downloading github.com/Anush008/fastembed-go v1.0.0
go: github.com/Anush008/fastembed-go@upgrade (v1.0.0) requires github.com/Anush008/fastembed-go@v1.0.0: parsing go.mod:
        module declares its path as: github.com/anush008/fastembed-go
                but was required as: github.com/Anush008/fastembed-go

[Anush008]

Thank you @miku.