More enemy and powerup types. (#52)

* WIP: bgf v0.1.7.

* Enable player to 1up spare lives.

* Add `powerup::OneUp` and powerup sfx.

* Check projectile bounds on both sides.

* Fixup spare lives display on HUD.

* Prepare for enemy rounds.

* Add `enemy::Trooper`.

* Move translation logic to `Enemy`.

* Nerf responsiveness when holding fire.

* Add `Trooper`, `Gunner`.

Add 1px border around sprite images.

* Cleanup, finalize bgf v0.1.7.

Author: karnkaul

CMakeLists.txt

@@ -11,9 +11,7 @@ include(FetchContent)
 FetchContent_Declare(
   bgf
   GIT_REPOSITORY https://github.com/karnkaul/bgf
-
-  # GIT_TAG v0.1.5
-  GIT_TAG adc217f
+  GIT_TAG v0.1.7
   SOURCE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/ext/bgf"
 )