Updated Termdash API (markdown)

Termdash-API.md

@@ -94,4 +94,31 @@ defer ctrl.Close()
 if err := ctrl.Redraw(); err != nil {
     return fmt.Errorf("ctrl.Redraw => %v", err)
 }
+```
+
+## [termdash.ErrorHandler](https://github.com/mum4k/termdash/blob/1c6947618b08ae236959763efd07278be5f03211/termdash.go#L64-L71):
+
+The **termdash.ErrorHandler** function is used to provide a custom error handler. If not provided, the application will panic on all runtime errors. An error handler is a function that receives the error and decides what to do. This function must be thread-safe, since Termdash delivers events concurrently.
+
+The following example shows initialisation of Termdash with an error handler that just logs the error message:
+
+```go
+// Create context ctx, terminal t and container c as in the examples above.
+
+// An error handler that just logs the error.
+eh := func(err error) {
+  log.Printf("Termdash runtime error: %v", err)
+}
+
+// When running Termdash via the Run function.
+if err := termdash.Run(ctx, t, c, termdash.ErrorHandler(eh)); err != nil {
+    return fmt.Errorf("termdash.Run => %v", err)
+}
+
+// When running Termdash via the Controller type.
+ctrl, err := termdash.NewController(t, c, termdash.ErrorHandler(eh))
+if err != nil {
+    return fmt.Errorf("termdash.NewController => %v", err)
+}
+defer ctrl.Close()
 ```