Add Handy / Funscript support (#1377)

* Add funscript route to scenes

Adds a /scene/:id/funscript route which serves a funscript file, if present.

Current convention is that these are files stored with the same path, but with the extension ".funscript".

* Look for funscript during scan

This is stored in the Scene record and used to drive UI changes for funscript support.

Currently, that's limited to a funscript link in the Scene's file info.

* Add filtering and sorting for interactive
* Add Handy connection key to interface config
* Add Handy client and placeholder component.

Uses defucilis/thehandy, but not thehandy-react as I had difficulty integrating the context with the existing components.

Instead, the expensive calculation for the server time offset is put in localStorage for reuse.

A debounce was added when scrubbing the video, as otherwise it spammed the Handy API with updates to the current offset.

pkg/manager/config/config.go

@@ -1,17 +1,16 @@
 package config
 
 import (
+	"errors"
 	"fmt"
+	"io/ioutil"
+	"path/filepath"
+	"regexp"
 	"runtime"
 	"strings"
 
 	"golang.org/x/crypto/bcrypt"
 
-	"errors"
-	"io/ioutil"
-	"path/filepath"
-	"regexp"
-
 	"github.com/spf13/viper"
 
 	"github.com/stashapp/stash/pkg/models"
@@ -123,6 +122,7 @@ const ShowStudioAsText = "show_studio_as_text"
 const CSSEnabled = "cssEnabled"
 const WallPlayback = "wall_playback"
 const SlideshowDelay = "slideshow_delay"
+const HandyKey = "handy_key"
 
 // DLNA options
 const DLNAServerName = "dlna.server_name"
@@ -633,6 +633,10 @@ func (i *Instance) GetCSSEnabled() bool {
 	return viper.GetBool(CSSEnabled)
 }
 
+func (i *Instance) GetHandyKey() string {
+	return viper.GetString(HandyKey)
+}
+
 // GetDLNAServerName returns the visible name of the DLNA server. If empty,
 // "stash" will be used.
 func (i *Instance) GetDLNAServerName() string {