Doesn't work with newer versions of the bootloader crate

[BSFishy]

Starting in version 0.10.1 of the bootloader crate, they removed the package.metadata.bootloader.target key in their Cargo.toml. This causes an error to be thrown by this crate whenever using a version of bootimage than version 0.10.0.

The error looks as follows:

Error: An error occured while trying to build the bootloader: The `bootloader` dependency has not the right format: No `package.metadata.bootloader.target` key found in Cargo.toml of bootloader

(If you're using the official bootloader crate, you need at least version 0.5.1)

Caused by:
    The `bootloader` dependency has not the right format: No `package.metadata.bootloader.target` key found in Cargo.toml of bootloader
    
    (If you're using the official bootloader crate, you need at least version 0.5.1)

Perhaps, for the time being, the error could include a message that a version higher than 0.10.0 cannot be used also, until a legitimate fix is created.

[BSFishy]

Just realized that post 0.10.0 of the bootloader crate doesn't use this project anymore. Reference for anyone who is looking at this in the future.