Add workaround for timezones on windows (#151)

Add workaround for timezones on windows

Co-authored-by: kolaente <k@knt.li>
Reviewed-on: https://kolaente.dev/vikunja/api/pulls/151

vendor/4d63.com/tz/tz.go

@@ -0,0 +1,38 @@
+// Package tz contains time zone info so that you can predictably load
+// Locations regardless of the locations available on the locally running
+// operating system.
+//
+// The stdlib time.LoadLocation function loads timezone data from the operating
+// system or from zoneinfo.zip in a local Go installation. Both of these are
+// often missing from some operating systems, especially Windows.
+//
+// This package has the zoneinfo.zip from Go embedded into the package so that
+// queries to load a location always return the same data regardless of
+// operating system.
+//
+// This package exists because of https://github.com/golang/go/issues/21881.
+package tz // import "4d63.com/tz"
+
+import (
+	"errors"
+	"time"
+)
+
+//go:generate rm -fr zoneinfo
+//go:generate unzip -q $GOROOT/lib/time/zoneinfo.zip -d zoneinfo/
+//go:generate go run 4d63.com/embedfiles -out=zoneinfo.go -pkg=tz zoneinfo/
+
+func tzData(name string) ([]byte, bool) {
+	data, ok := files["zoneinfo/"+name]
+	return data, ok
+}
+
+func LoadLocation(name string) (*time.Location, error) {
+	if name == "" || name == "UTC" || name == "Local" {
+		return time.LoadLocation(name)
+	}
+	if tzdata, ok := tzData(name); ok {
+		return time.LoadLocationFromTZData(name, tzdata)
+	}
+	return nil, errors.New("unknown location " + name)
+}