goimports
* Add `goimports` lint. * Fix `goimports` issue. * Fix group to `github.com/scroll-tech/go-thereum`.
* Update mod file and all imports to use scroll-tech URL Fixes #14 * Update Discord link
This commit: - Adds a --msgfile option to read the message to sign from a file instead of command line argument. - Adds a unit test for signing subcommands. - Removes some weird whitespace in the code.