new cmd: block new <blockType> <labels>...

[niraj8]

i was looking for a way to add root blocks to an hcl file.
found this comment in an issue #88 (comment)

the tests i have added are very terraform specific and the hcledit block new <blockType> <labels> may not be the best way to nest this cmd.

let me know in case there's any suggestions to make this better.

[minamijoyo]

Hi, @niraj8 Thank you for your contribution! LGTM 👍

FYI:
As an alternative, I considered extending the block append command and adding a special notation, e.g., Top-level dot ., to indicate File as the parent address. However, I was not convinced. Since address notation is not in the HCL specification and such notation is not widely used in any HCL applications, I rejected this idea, thinking it would be better not to add a new special notation.

[minamijoyo]

While updating the README, I noticed it might be better to have an optional --newline flag that appends a new line before a new block, similar to the block append command.

[minamijoyo]

A subsequent PR #110 has changed the way arguments are received.