add a script to plot results from `bench_commit`

scripts/plot/bench_commit.py

+# ## usage
+# ```nushell
+# let res = cargo run --example bench_commit
+#     | lines
+#     | parse "{curve}: {degree} -> {t}"
+#     | into int degree
+#     | update t { into int | into duration }
+#
+# python scripts/plot/bench_commit.py (
+#     $res | group-by curve --to-table | update items { reject curve } | to json
+# )
+# ```
+import json
+import sys
+import matplotlib.pyplot as plt
+
+NB_NS_IN_MS = 1e6
+
+
+if __name__ == "__main__":
+    data = json.loads(sys.argv[1])
+
+    for group in data:
+        xs = [x["degree"] for x in group["items"]]
+        ys = [x["t"] / NB_NS_IN_MS for x in group["items"]]
+
+        plt.plot(xs, ys, label=group["group"], marker='o')
+
+    plt.xlabel("degree")
+    plt.ylabel("time (in ns)")
+
+    plt.title("time to commit polynomials for certain curves")
+
+    plt.legend()
+    plt.grid(True)
+    plt.show()