Fix typos (#904)

Author: vshev4enko

lib/sentry.ex

@@ -46,7 +46,7 @@ defmodule Sentry do
   not uncommon for most applications to have a "staging" environment. In order
   to handle this without adding an additional Mix environment, you can set an
   environment variable that determines the release level. By default, Sentry
-  picks up the `SENTRY_ENVIRONMENT` variable (*at runtime, when starging*).
+  picks up the `SENTRY_ENVIRONMENT` variable (*at runtime, when starting*).
   Otherwise, you can read the variable at runtime. Do this only in
   `config/runtime.exs` so that it will work both for local development as well
   as Mix releases.

lib/sentry/config.ex

@@ -357,7 +357,7 @@ defmodule Sentry.Config do
       default: [],
       type_doc: "list of `t:Path.t/0`",
       doc: """
-      Aa list of paths to the root of
+      A list of paths to the root of
       your application's source code. This is used to determine the relative
       path of files in stack traces. Usually, you'll want to set this to
       `[File.cwd!()]`. For umbrella apps, you should set this to all the application