Add support for Nushell env var settings

Currently, swiftly incorrectly generates Bash env var scripts when it is installed in Nushell.

Author: MaxDesiatov

Sources/Swiftly/Init.swift

@@ -156,6 +156,15 @@ struct Init: SwiftlyCommand {
                     set -x PATH "$SWIFTLY_BIN_DIR" $PATH
                 end
 
+                """
+            } else shell.hasSuffix("/nu") {
+                env = """
+                $env.SWIFTLY_HOME_DIR = "\(Swiftly.currentPlatform.swiftlyHomeDir.path)"
+                $env.SWIFTLY_BIN_DIR = "\(Swiftly.currentPlatform.swiftlyBinDir.path)"
+                if "$SWIFTLY_BIN_DIR" not-in $env.PATH {
+                    $env.PATH = ($env.PATH | split row (char esep) | prepend $env.SWIFTLY_BIN_DIR)
+                }
+
                 """
             } else {
                 env = """