add P1 mass form

operators.toml

@@ -31,3 +31,11 @@ dimensions    = [2, 3]
 quadrature    = 2
 loop-strategy = "sawtooth"
 optimizations = ["moveconstants", "vectorize", "quadloops", "sym_loc_mat"]
+
+[[mass]]
+trial-space   = "P1"
+test-space    = "P1"
+dimensions    = [2, 3]
+quadrature    = 2
+loop-strategy = "sawtooth"
+optimizations = ["moveconstants", "vectorize", "quadloops", "sym_loc_mat", "tabulate"]