Add test scenario to tax2gas

x/tax2gas/README.md

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+# Tax2gas
+
+## Testcases
+
+- Normal tx success
+- Not supported tx will not be deducted tax amount
+- Forward tx should minus the amount to tx origin
+- Multiple forward works
+- Out of gas should return the tax and not consumed gas
+- Error forward tx should return the fund
+- Multiple msg types should works
+- Grant msg should work
+- Allow pay with multiple fees should work
+
+| No | Name | Scenario | Expect Result | Covered by |
+|----|----------|-------------------|---------------|------------|
+| 1 | Normal transaction should success | User transfer or make some special transactions which send coins to different address | Tax should be deducted with correct amount| |
+| 2 | Not supported tx will not be deducted tax amount | User transfer or make some special transactions that not in the tax list | Tax shouldn't be deducted with correct amount| |
+| 3 | Forward transaction should deduct the amount to tx origin | User execute contract that will trigger an execute msg to another contract | - User should be the tx origin of the execute msg<br>- Tax should be deducted with correct amount | |
+| 4 | Multiple forward works | Contracts will trigger another contracts multiple times | - User should be the tx origin of the execute msg<br>- Tax should be deducted with correct amount | |
+| 5 | Out of gas should return the tax and not consumed gas | User make some transactions with limited gas amount that will lead to cause `out of gas` error | Tax and not consumed gas should be revert to user | |
+| 6 | Error forward tx should return the tax and not consumed gas | User execute contract that will trigger an execute msg to another contract. The execute msg to another contract will be failed | Tax and not consumed gas should be revert to user | |
+| 7 | Multiple msg types should works | - Test multiple tx type that's in the tax list or not <br>- Contract dispatch multiple tx types | Chain will deduct tax with correct amount | |
+| 8 | Grant msg should work | User grant multiple type of permissions to different transactions | Grant permission msg will only can deduct with one denom | |
+| 9 | Allow pay with multiple fees should work | User make transaction with multiple coins as fee | Fee can be paid by multiple denom, if one denom is not enough, then it will deduct other denom | |