when running dotenvx convert write original .env* file to .env*.previous

[motdotla]

this way if there is an edge case bug with encryptme (we haven't tested all edge cases yet), the user does not lose their important .env data.

[motdotla]

i think should be unnecessary if we get all edge cases covered. it adds so much noise.

[bingtsingw]

Maybe we can make convert command more general to convert to or from encrypted data:
dotenvx convert --encrypt -f .env.xxx -o .env.xxx.encrypted
dotenvx convert --decrypt -f .env.xxx.encrypted -o .env.xxx

--encrypt and -o can be designed as optional to be compatible with current command