Feature: Improved checksum support for bump-recipe

[ShalokShalom]

Hi there 🙂

bump-recipe is a lovely app, very neat to have such a tool 😊

Currently, it does not do the following:

.) Fill in the checksum if one is not provided yet.
.) Fill in the checksum if the app is already the newest version.

That means it cannot be used to initially create a new program.

I suggest that this new feature to be added.

[wolfv]

It's not so simple unfortunately, because there is no good YAML parser in Rust that supports parsing and emitting YAML with comments and all metadata intact - which is why we use string replacement ofr the SHA hash.

The safest bet would be to add a empty SHA hash in the source or some other random hash.