feat(examples): grc20 refactor

examples/gno.land/p/demo/grc/grc20/examples_test.gno

@@ -0,0 +1,18 @@
+package grc20
+
+// XXX: write Examples
+
+func ExampleInit()                            {}
+func ExampleExposeBankForMaketxRunOrImports() {}
+func ExampleCustomGRC20Impl()                 {}
+func ExampleAllowance()                       {}
+func ExampleRealmBanker()                     {}
+func ExamplePrevRealmBanker()                 {}
+func ExampleAccountBanker()                   {}
+func ExampleTransfer()                        {}
+func ExampleApprove()                         {}
+func ExampleTransferFrom()                    {}
+func ExampleMint()                            {}
+func ExampleBurn()                            {}
+
+// ...

examples/gno.land/p/demo/grc/grc20/gno.mod

@@ -4,6 +4,7 @@ require (
 	gno.land/p/demo/avl v0.0.0-latest
 	gno.land/p/demo/grc/exts v0.0.0-latest
 	gno.land/p/demo/testutils v0.0.0-latest
+	gno.land/p/demo/uassert v0.0.0-latest
 	gno.land/p/demo/ufmt v0.0.0-latest
 	gno.land/p/demo/urequire v0.0.0-latest
 )

examples/gno.land/p/demo/grc/grc20/mock.gno

@@ -0,0 +1,3 @@
+package grc20
+
+// XXX: func Mock(t *Token)