Fix linux release process

Update to swift-syntax from Swift 5.9

Use Keith's magic library on macOS (#274)

fixup! fixup! fixup! fixup! make fancy please

Upgrade to Swift 5.5 (#252)

Rename variable name

Bump Linux Swift to 5.3.2

Include completion scripts in Darwin package

Bump version to 0.4.1

### Changes

- Supports Swift 5.2 syntax, which also means the project requires 5.2 to build.
- For boolean options, instead of specifying negative value with `false` following the flag on the command
  line, a new corresponding negative flag should be used. For example, previously, not ignoring docstring
  section for `throws` can be specified by `--ignore-throws false`. Now it should be `--no-ignore-throws`.
  The help texts for all boolean commands have been updated to reflect this.

### New

- Similar to boolean options, now there's negative flags to override repeatable values on the command line.
  Example: `--no-needs-separation` will negate any `needs-separation` values.