Improve particles and VFX, add blob shadow below player and enemies (#180)

- Add projector light textures.
- Tweak the flying forklift's dynamic light and particles to be more noticeable.
- Add bullet impact particles with collision against level geometry
  (using a generated SDF).
- Don't use fixed FPS and disable interpolation to make particles smoother
  (trails aren't used, so fixed FPS isn't strictly needed).
- Add proximity fade to some particles to smooth out the transition
  with solid geometry.
- Fix some particles being shaded when they should be unshaded.
- Reduce crosshair size to be more subtle while aiming.

effects_shared/blob_shadow.tres

@@ -0,0 +1,12 @@
+[gd_resource type="GradientTexture2D" load_steps=2 format=3 uid="uid://8d78kbpqjumj"]
+
+[sub_resource type="Gradient" id="Gradient_m6m55"]
+interpolation_mode = 2
+offsets = PackedFloat32Array(0, 0.2, 1)
+colors = PackedColorArray(0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0)
+
+[resource]
+gradient = SubResource("Gradient_m6m55")
+fill = 1
+fill_from = Vector2(0.5, 0.5)
+fill_to = Vector2(0.5, 0.01)

effects_shared/spotlight_projector.png.import

@@ -0,0 +1,34 @@
+[remap]
+
+importer="texture"
+type="CompressedTexture2D"
+uid="uid://biye81cs18sdp"
+path="res://.godot/imported/spotlight_projector.png-df51635ec657a5f50f175250c2209b0c.ctex"
+metadata={
+"vram_texture": false
+}
+
+[deps]
+
+source_file="res://effects_shared/spotlight_projector.png"
+dest_files=["res://.godot/imported/spotlight_projector.png-df51635ec657a5f50f175250c2209b0c.ctex"]
+
+[params]
+
+compress/mode=0
+compress/high_quality=false
+compress/lossy_quality=0.7
+compress/hdr_compression=1
+compress/normal_map=0
+compress/channel_pack=0
+mipmaps/generate=false
+mipmaps/limit=-1
+roughness/mode=0
+roughness/src_normal=""
+process/fix_alpha_border=true
+process/premult_alpha=false
+process/normal_map_invert_y=false
+process/hdr_as_srgb=false
+process/hdr_clamp_exposure=false
+process/size_limit=0
+detect_3d/compress_to=1