docs: also document config options for hexdocs

lib/tower.ex

@@ -17,7 +17,6 @@ defmodule Tower do
       - [`tower_rollbar`](https://hexdocs.pm/tower_rollbar)
       - [`tower_sentry`](https://hexdocs.pm/tower_sentry)
       - [`tower_slack`](https://hexdocs.pm/tower_slack)
-      - more coming...
 
   ## Motivation
 
@@ -199,6 +198,76 @@ defmodule Tower do
 
       # in some config/*.exs
       config :tower, reporters: [MyApp.ErrorReporter]
+
+  ## Configuration
+
+  ### `reporters`
+
+  List of reporters Tower should report events to.
+
+  Default: `[Tower.EphemeralReporter]`
+
+  Example:
+
+  ```elixir
+  config :tower, reporters: [TowerEmail]
+  ```
+
+  ### `log_level`
+
+  `Logger` messages this level and above will be reported.
+
+  Possible values are any of defined `Logger` levels (https://hexdocs.pm/logger/Logger.html#module-levels) or
+  `:none` to disable reporting of `Logger` messages.
+
+  Default: `:critical`
+
+  Example:
+
+  ```elixir
+  config :tower, log_level: :error
+  ```
+
+  ### `ignored_exceptions`
+
+  List of exceptions that Tower should ignore and not report.
+
+  Default: `[]`
+
+  Example:
+
+  ```elixir
+  config :tower, ignored_exceptions: [DBConnection.ConnectionError]
+  ```
+
+  ### `logger_metadata`
+
+  List of keys that Tower should pick up from the current process `Logger.metadata` when reporting events.
+
+  Default: `[]`
+
+  Example:
+
+  A common use case is setting `Logger.metadata(user_id: user.id)` at the start of your plugs or controller actions and
+  configure Tower:
+
+  ```elixir
+  config :tower, logger_metadata: [:user_id]
+  ```
+
+  so that it's included in the reported exception or message event as extra metadata.
+
+  Also if using Phoenix you can
+
+  ```elixir
+  config :tower, logger_metadata: [:request_id]
+  ```
+
+  so that you can co-relate your exceptions reports to the request id in your application logs.
+
+  More about Logger metadata:
+   - https://hexdocs.pm/logger/Logger.html#module-metadata
+   - https://hexdocs.pm/logger/Logger.html#metadata/1
   """
 
   defmodule ReportEventError do