Use multiple versions of fec builder

# Install v1.x
npm i fec-builder-1@npm:fec-builder@v1.18.0-beta.2 -g

# Check location of bin file & rename it
which fec-builder # /usr/local/bin/fec-builder-1
mv /usr/local/bin/fec-builder /usr/local/bin/fec-builder-1

# Install v2.x
npm i fec-builder -g

# Done & check result
fec-builder-1 --version # 1.18.0-beta.2
fec-builder --version # 2.1.2