Add support for apple silicon/darwin-arm64 (#106)

Makefile

@@ -44,6 +44,9 @@ browserpass-arm64: *.go **/*.go
 browserpass-darwin64: *.go **/*.go
 	env GOOS=darwin GOARCH=amd64 go build -o $@
 
+browserpass-darwin-arm64: *.go **/*.go
+	env GOOS=darwin GOARCH=arm64 go build -o $@
+
 browserpass-openbsd64: *.go **/*.go
 	env GOOS=openbsd GOARCH=amd64 go build -o $@
 
@@ -75,7 +78,7 @@ clean:
 	rm -rf vendor
 
 .PHONY: dist
-dist: clean vendor browserpass-linux64 browserpass-arm browserpass-arm64 browserpass-darwin64 browserpass-openbsd64 browserpass-freebsd64 browserpass-windows64
+dist: clean vendor browserpass-linux64 browserpass-arm browserpass-arm64 browserpass-darwin64 browserpass-darwin-arm64 browserpass-openbsd64 browserpass-freebsd64 browserpass-windows64
 	$(eval TMP := $(shell mktemp -d))
 
 	# Full source code
@@ -84,7 +87,7 @@ dist: clean vendor browserpass-linux64 browserpass-arm browserpass-arm64 browser
 	(cd "$(TMP)" && tar -cvzf "browserpass-native-$(VERSION)-src.tar.gz" "browserpass-native-$(VERSION)")
 
 	# Unix installers
-	for os in linux64 arm arm64 darwin64 openbsd64 freebsd64; do \
+	for os in linux64 arm arm64 darwin64 darwin-arm64 openbsd64 freebsd64; do \
 	    mkdir $(TMP)/browserpass-"$$os"-$(VERSION); \
 	    cp -a browserpass-"$$os"* browser-files Makefile README.md LICENSE $(TMP)/browserpass-"$$os"-$(VERSION); \
         (cd $(TMP) && tar -cvzf browserpass-"$$os"-$(VERSION).tar.gz browserpass-"$$os"-$(VERSION)); \