[Dockerfile] Replace `ADD` in favor of `COPY`
[Dockerfile] Replace `ADD` in favor of `COPY`

`COPY` should always be the "go-to" instruction as it's more transparent than `ADD`

pH7Software/pH7-Social-Dating-CMS,pH7Software/pH7-Social-Dating-CMS,pH7Software/pH7-Social-Dating-CMS,pH7Software/pH7-Social-Dating-CMS