✨ feat: add Midjourney (#138)

* 🚧 stash

* ✨ feat: add Midjourney

* 📝 doc: update readme

providers/midjourney/constant.go

@@ -0,0 +1,69 @@
+// Author: Calcium-Ion
+// GitHub: https://github.com/Calcium-Ion/new-api
+// Path: relay/constant/relay_mode.go
+package midjourney
+
+const (
+	RelayModeUnknown = iota
+	RelayModeMidjourneyImagine
+	RelayModeMidjourneyDescribe
+	RelayModeMidjourneyBlend
+	RelayModeMidjourneyChange
+	RelayModeMidjourneySimpleChange
+	RelayModeMidjourneyNotify
+	RelayModeMidjourneyTaskFetch
+	RelayModeMidjourneyTaskImageSeed
+	RelayModeMidjourneyTaskFetchByCondition
+	RelayModeAudioSpeech
+	RelayModeAudioTranscription
+	RelayModeAudioTranslation
+	RelayModeMidjourneyAction
+	RelayModeMidjourneyModal
+	RelayModeMidjourneyShorten
+	RelayModeMidjourneySwapFace
+)
+
+// Author: Calcium-Ion
+// GitHub: https://github.com/Calcium-Ion/new-api
+// Path: constant/midjourney.go
+
+const (
+	MjErrorUnknown = 5
+	MjRequestError = 4
+)
+
+const (
+	MjActionImagine       = "IMAGINE"
+	MjActionDescribe      = "DESCRIBE"
+	MjActionBlend         = "BLEND"
+	MjActionUpscale       = "UPSCALE"
+	MjActionVariation     = "VARIATION"
+	MjActionReRoll        = "REROLL"
+	MjActionInPaint       = "INPAINT"
+	MjActionModal         = "MODAL"
+	MjActionZoom          = "ZOOM"
+	MjActionCustomZoom    = "CUSTOM_ZOOM"
+	MjActionShorten       = "SHORTEN"
+	MjActionHighVariation = "HIGH_VARIATION"
+	MjActionLowVariation  = "LOW_VARIATION"
+	MjActionPan           = "PAN"
+	MjActionSwapFace      = "SWAP_FACE"
+)
+
+var MidjourneyModel2Action = map[string]string{
+	"mj_imagine":        MjActionImagine,
+	"mj_describe":       MjActionDescribe,
+	"mj_blend":          MjActionBlend,
+	"mj_upscale":        MjActionUpscale,
+	"mj_variation":      MjActionVariation,
+	"mj_reroll":         MjActionReRoll,
+	"mj_modal":          MjActionModal,
+	"mj_inpaint":        MjActionInPaint,
+	"mj_zoom":           MjActionZoom,
+	"mj_custom_zoom":    MjActionCustomZoom,
+	"mj_shorten":        MjActionShorten,
+	"mj_high_variation": MjActionHighVariation,
+	"mj_low_variation":  MjActionLowVariation,
+	"mj_pan":            MjActionPan,
+	"swap_face":         MjActionSwapFace,
+}