chores: add readme for BEP-127 tool

docs/parlia/README-BEP-127.md

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+## BEP-127: Temporary Maintenance Mode for Validators
+
+Temporary Maintenance is supposed to last one or a few hours. The validator seat will be temporarily dropped from the block producing rotation during the maintenance. Since long-time offline maintenance is not encouraged, the validator will still be slashed if the maintenance lasts too long. To lower the impact from poorly-operating validators who forget to claim its maintenance, they will be forced to enter Temporary Maintenance mode too.
+
+- **enterMaintenance**: Validator can claim itself to enter scheduled maintenance by sending a transaction signed by the consensus key. 
+- **exitMaintenance**: The validator can claim itself to exit maintenance by sending another transaction.
+
+More details in [BEP-127](https://github.com/bnb-chain/BEPs/blob/master/BEP127.md).
+
+
+## How to enter/exit maintenance
+
+### Running `geth`
+make sure you have unlocked the consensus address of your validator
+
+### Running `built-in interactive`
+```shell
+$ geth attach geth.ipc
+```
+
+This command will:
+* Start up `geth`'s built-in interactive [JavaScript console](https://geth.ethereum.org/docs/interface/javascript-console),
+  (via the trailing `console` subcommand) through which you can interact using [`web3` methods](https://web3js.readthedocs.io/en/)
+  (note: the `web3` version bundled within `geth` is very old, and not up to date with official docs),
+  as well as `geth`'s own [management APIs](https://geth.ethereum.org/docs/rpc/server).
+
+
+### enter maintenance
+```
+web3.eth.sendTransaction({
+   from: "consensus address of your validator",
+   to: "0x0000000000000000000000000000000000001000",
+   data: "0x9369d7de"
+})
+```
+
+### exit maintenance
+```
+web3.eth.sendTransaction({
+   from: "consensus address of your validator",
+   to: "0x0000000000000000000000000000000000001000",
+   data: "0x04c4fec6"
+})
+```
+
+
+