doc: Fix customAuthenticationProvider documentation (#1683)

README.md

@@ -524,9 +524,16 @@ only enabled with the `--ignoreJWTSignature` flag. Make sure to only set this fl
 
 ### Serverless plugin authorizers
 
-If your authentication needs are custom and not satisfied by the existing capabilities of the Serverless offline project, you can inject your own authentication strategy. To inject a custom strategy for Lambda invocation, you define a custom variable under `serverless-offline` called `authenticationProvider` in the serverless.yml file. The value of the custom variable will be used to `require(your authenticationProvider value)` where the location is expected to return a function with the following signature.
+If your authentication needs are custom and not satisfied by the existing capabilities of the Serverless offline project, you can inject your own authentication strategy. To inject a custom strategy for Lambda invocation, you define a custom variable under `offline` called `customAuthenticationProvider` in the serverless.yml file. The value of the custom variable will be used to `require(your customAuthenticationProvider value)` where the location is expected to return a function with the following signature.
+
+```yaml
+  offline:
+    customAuthenticationProvider: ./path/to/custom-authentication-provider
+```
 
 ```js
+// ./path/to/customer-authentication-provider.js
+
 module.exports = function (endpoint, functionKey, method, path) {
   return {
     getAuthenticateFunction() {
@@ -543,7 +550,7 @@ module.exports = function (endpoint, functionKey, method, path) {
 }
 ```
 
-A working example of injecting a custom authorization provider can be found in the projects integration tests under the folder `custom-authentication`.
+A working example of injecting a custom authorization provider can be found in the projects integration tests under the folder [`custom-authentication`](./tests/integration/custom-authentication).
 
 ## Custom headers