output documentation: Add examples of FLBRegisterPluginWithEventType

This change adds to the README.md files of each example output plugin
and example of how to enable metric usage using the new function
`FLBRegisterPluginWithEventType`

Signed-off-by: jmccormick7 <[email protected]>

Author: jmccormick7

examples/out_gstdout/README.md

@@ -24,6 +24,18 @@ func FLBPluginRegister(ctx unsafe.Pointer) int {
 
 This function is invoked at start time _before_ any configuration is done inside the engine.
 
+### Setting event type 
+
+By default, Fluent Bit Golang plugins process logs. Optionally, the event_type 
+can be set to allow for metrics by using `output.FLBPluginRegisterWithEventType`. 
+
+```go
+//export FLBPluginRegister 
+func FLBPluginRegister(def unsafe.Pointer) int {
+	return output.FLBPluginRegisterWithEventType(ctx, output.FLB_OUTPUT_METRICS, "gstdout", "Stdout GO!")
+}
+```
+
 ## Plugin Initialization
 
 Before the engine starts, it initialize all plugins that were requested to start. Upon initialization a configuration context already exists, so the plugin can ask for configuration parameters or do any other internal checks. E.g:

examples/out_multiinstance/README.md

@@ -29,6 +29,18 @@ func FLBPluginRegister(def unsafe.Pointer) int {
 This function is invoked at start time _before_ any configuration is done
 inside the engine.
 
+### Setting event type 
+
+By default, Fluent Bit Golang plugins process logs. Optionally, the event_type 
+can be set to allow for metrics by using `output.FLBPluginRegisterWithEventType`. 
+
+```go
+//export FLBPluginRegister 
+func FLBPluginRegister(def unsafe.Pointer) int {
+	return output.FLBPluginRegisterWithEventType(ctx, output.FLB_OUTPUT_METRICS, "multiinstance", "Testing multiple instances")
+}
+```
+
 ## Plugin Initialization
 
 Before the engine starts, it initializes all plugins that were configured.