Added . in ReadMe (Using Ward inside docker)

[OceanTechnic]

Without . docker will not build the image

From: docker build --tag ward

TO: docker build . --tag ward

[YueMiyuki]

Yes, it need to know that the dockerfile is in the current path and build it, but i will recommand docker build --tag ward . because it looks more neat

[OceanTechnic]

@ItzMiracleOwO I added the . at the end