Bash aliases

Set aliases to set specific versions of packages to be called for bash commands

Example:

alias python3=python3.9
alias pip3='python3.9 -m pip'
alias pip=pip3

Sets python3 to use the python3.9 installation (instead of, for example, python3.8 if that is also installed)
Sets pip3 to use the pip installation that is in the python3.9 installation (instead of, for example, the pip instalalation that sits within the python3.8 installation)
Sets pip to call pip3