Import howett.net/plist by its correct name

Also bumping the version to one with a go.mod.

vendor/howett.net/plist/README.md

@@ -0,0 +1,21 @@
+# plist - A pure Go property list transcoder [![coverage report](https://gitlab.howett.net/go/plist/badges/master/coverage.svg)](https://gitlab.howett.net/go/plist/commits/master)
+## INSTALL
+```
+$ go get howett.net/plist
+```
+
+## FEATURES
+* Supports encoding/decoding property lists (Apple XML, Apple Binary, OpenStep and GNUStep) from/to arbitrary Go types
+
+## USE
+```go
+package main
+import (
+	"howett.net/plist"
+	"os"
+)
+func main() {
+	encoder := plist.NewEncoder(os.Stdout)
+	encoder.Encode(map[string]string{"hello": "world"})
+}
+```