Add parameter to allow changing the cdktf synth output

[garysassano]

It could be beneficial to introduce an option in the .projenrc file to switch the cdktf synth result from its standard JSON output format to HCL output. This can be achieved by incorporating the --hcl flag during the synth invocation. Additionally, it may be necessary to implement a validation step to ensure that the cdktfVersion specified is at least 0.20 before this HCL option can be enabled.