Recommend installation using Pipx

[MaddyGuthridge]

Currently, the instructions in README.md recommend installing Rmview using Pip, which can cause issues due to conflicting package versions (some tools I need to use for work have break rmview each time they are updated).

To avoid these issues, and ensure Rmview is installed in an isolated virtual environment, the README should recommend installation using Pipx, which creates a new virtual environment for the project automatically.