move-migrations-to-option (#1)

Removes global variables and sets up migrations as optional.

Reviewed-on: #1
Co-authored-by: Mason Payne <mason@masonitestudios.com>
Co-committed-by: Mason Payne <mason@masonitestudios.com>

examples/basic-usage/main.go

@@ -17,9 +17,9 @@ func main() {
 	// Open the database
 	tdb, err := libsqldb.NewLibSqlDB(
 		primaryUrl,
-		migrationFiles,
+		libsqldb.WithMigrationFiles(migrationFiles),
 		libsqldb.WithAuthToken(authToken),
-		libsqldb.WithLocalDBName("local.db"),
+		libsqldb.WithLocalDBName("local.db"), // will not be used for remote-only
 	)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "failed to open db %s: %s", primaryUrl, err)