Fix broken release: add hex_packages.exs to package files

Author: mat-hek

CHANGELOG.md

@@ -1,4 +1,8 @@
 # Changelog
+
+## 1.2.6
+Fix broken 1.2.5 release [#1043](https://github.com/membraneframework/membrane_core/pull/1043)
+
 ## 1.2.5 
  * Add tutorials [#1007](https://github.com/membraneframework/membrane_core/pull/1007), plugins [#1012](https://github.com/membraneframework/membrane_core/pull/1012) and demos [#1013](https://github.com/membraneframework/membrane_core/pull/1013) to the docs.
  * Avoid division by 0 in stalker under weird timer behaviour [#1035](https://github.com/membraneframework/membrane_core/pull/1035)

mix.exs

@@ -1,8 +1,9 @@
 defmodule Membrane.Mixfile do
   use Mix.Project
 
-  @version "1.2.5"
+  @version "1.2.6"
   @source_ref "v#{@version}"
+  @hex_packages_path "scripts/elixir/hex_packages.exs"
 
   def project do
     [
@@ -111,7 +112,7 @@ defmodule Membrane.Mixfile do
   end
 
   defp packages_in_ecosystem do
-    {packages, _bindings} = Code.eval_file("scripts/elixir/hex_packages.exs")
+    {packages, _bindings} = Code.eval_file(@hex_packages_path)
     packages
   end
 
@@ -236,7 +237,8 @@ defmodule Membrane.Mixfile do
       links: %{
         "GitHub" => link(),
         "Membrane Framework Homepage" => "https://membrane.stream"
-      }
+      },
+      files: ~w"lib .formatter.exs mix.exs README* LICENSE* CHANGELOG* #{@hex_packages_path}"
     ]
   end