refactor: transparent render (#14)

* fix(renderer): defer uniform location retrieval and add view matrix in outline rendering

* refactor(gameplay): encapsulate per-type vertex data into VertexData struct

* feat(rendering): separate transparent blocks into discard and blend modes

* feat(renderer): implement order-independent transparency

* fix(shaders): reduce alpha discard threshold to 0.8

assets/data/block/grass.toml

@@ -1,5 +1,7 @@
 id = 9
+is_blend = false
 is_cross_plane = true
+is_discard = true
 is_gas = false
 is_liquid = false
 is_passable = true