[example] Update gallery images (taichi-dev#7053)

This PR updates the `ti gallery` UI. Must be merged after the gallery
image is updated in the assets repo:
taichi-dev/taichi_assets#4

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

python/taichi/_main.py

@@ -147,7 +147,7 @@ def gallery(self, arguments: list = sys.argv[2:]):
         slide_bar = 14
         top_margin = 6
         left_margin = 7
-        bottom_margin = 23
+        bottom_margin = 32
         row_spacing = 32
         col_spacing = 11
         tile_size = 128
@@ -168,7 +168,9 @@ def gallery(self, arguments: list = sys.argv[2:]):
         dy = tile_size / height
 
         examples = [
-            "sdf_renderer", "cornell_box", "rasterizer", "euler", "fractal",
+            "poisson_disk_sampling", "mass_spring_3d_ggui",
+            "circle_packing_image", "snow_phaseField", "sdf_renderer",
+            "cornell_box", "karman_vortex_street", "euler", "fractal",
             "mpm128", "pbf2d", "mass_spring_game"
         ]