Add syntax_tools to extra_applications to fix compilation on Elixir 1.15

[michallepicki]

I saw somewhere a mention that this is a compile-only dependency? Unfortunately I don't know how it should be declared to be present during compilation but not when application starts. Maybe this is what syntax_tools: :optional in :extra_applications would do but I haven't tested building a release with this value.

[KiKoS0]

I have the same issue compiling with Elixir 1.15. I tried building a release with syntax_tools: :optional but :epp_dodger was still bundled in it. Is it fine to merge this to unblock upgrades until a better way to achieve this is found?

[wojtekmach]

I have reported this upstream: elixir-lang/elixir#12622

[wojtekmach]

I have submitted a proper fix: #60

[michallepicki]

Closing in favor of #60

[voltone]

I released v0.8.7 with the fix from #60. Thanks @wojtekmach !