Hi

We are currently on elixir 1.14.3, we import matrix dependency: `{:matrix, "~> 0.3.0"},`

After upgrading to 1.15.6 there is now an error by starting the application:

```
error: undefined variable "description"
/home/me/project/deps/matrix/mix.exs:7: Matrix.Mixfile.project/0
error: undefined variable "package"
/home/me/project/deps/matrix/mix.exs:8: Matrix.Mixfile.project/0
error: undefined variable "deps"
/home/me/project/deps/matrix/mix.exs:10: Matrix.Mixfile.project/0
warning: function deps/0 is unused
/home/me/project/deps/matrix/mix.exs:21: Matrix.Mixfile (module)
warning: function description/0 is unused
/home/me/project/deps/matrix/mix.exs:26: Matrix.Mixfile (module)
warning: function package/0 is unused
/home/me/project/deps/matrix/mix.exs:33: Matrix.Mixfile (module)
Error while loading project :matrix at /home/me/project/deps/matrix
** (CompileError) deps/matrix/mix.exs: cannot compile module Matrix.Mixfile (errors have been logged)
```

Looking at deps/matrix/mix.exs I can see

```
def project do
[app: :matrix,
version: "0.3.2",
description: description,
package: package,
elixir: "~> 1.1",
deps: deps,
docs: [extras: []]]
end
```

Now if I turn it to:

```
def project do
[app: :matrix,
version: "0.3.2",
description: description(),
package: package(),
elixir: "~> 1.1",
deps: deps(),
docs: [extras: []]]
end
```

(just for fun, i.e. calling functions instead) then it compiles.

So it looks like the dependency should be upgraded to support elixir 1.15, or did I misunderstood? I am asking because I cannot find the dependency github, so we probably will have to use another dependency for matrix.

Thx!