Add initial implementation of *arr service client

- Created `client.go` for the main client structure and methods to interact with *arr services.
- Added `types.go` to define data structures for system status, movies, and series.
- Implemented `radarr.go` for Radarr-specific client methods including health checks and movie retrieval.
- Introduced `interfaces.go` to define service interfaces for common operations across *arr services.
- Established a basic `main.go` for application entry point.
- Included a tutorial markdown file to guide users through building the client and understanding Go concepts.
- Initialized `go.mod` for module management.
- Organized code into appropriate packages for better structure and maintainability.

types.go

@@ -0,0 +1,45 @@
+package main
+
+import "time"
+
+type SystemStatus struct {
+	Version           string `json:"version"`
+	BuildTime         string `json:"buildTime"`
+	IsDebug           bool   `json:"isDebug"`
+	IsProduction      bool   `json:"isProduction"`
+	IsAdmin           bool   `json:"isAdmin"`
+	IsUserInteractive bool   `json:"isUserInteractive"`
+	StartupPath       string `json:"startupPath"`
+	AppData           string `json:"appData"`
+	OsName            string `json:"osName"`
+	OSVersion         string `json:"osVersion"`
+}
+
+type Movie struct {
+	ID               int       `json:"id"`
+	Title            string    `json:"title"`
+	Year             int       `json:"year"`
+	Path             string    `json:"path"`
+	Monitored        bool      `json:"monitored"`
+	Added            time.Time `json:"added"`
+	QualityProfileID int       `json:"qualityProfileId"`
+	ImdbID           string    `json:"imdbId"`
+	RmdbID           int       `json:"tmdbId"`
+}
+
+type Series struct {
+	ID               int       `json:"id"`
+	Title            string    `json:"title"`
+	Year             int       `json:"year"`
+	Path             string    `json:"path"`
+	Monitored        bool      `json:"monitored"`
+	Added            time.Time `json:"added"`
+	QualityProfileID int       `json:"qualityProfileId"`
+	TvdbID           int       `json:"tvdbId"`
+	Seasons          []Season  `json:"seasons"`
+}
+
+type Season struct {
+	SeasonNumber int  `json:"seasonNumber"`
+	Monitored    bool `json:"monitored"`
+}