feat: optimize canEnterMaintenance check

chore: modify var name

chore: optimize code

chore: remove unused comment

chore: remove unused comment

chore: optimize code style

feat: use _safeTransferBNB instead to.transfer

chore: remove unused line

feat: add getSlashThresholds for SlashIndicator and slashCount for BSCValidatorSet

feat: remove unused code

feat: add getSlashThresholds for SlashIndicator

chore: optimize code lint

feat: add _forceMaintainingValidatorsExit in updateValidatorSet

chore: add comments

feat: add maxNumOfMaintaining, maintainSlashScale params

fix numOfFelony check while all validators exit maintenance

fix: review comments

fix: maintainInfo.index issue, use 0 as a `sentinel value`

chore: modify comments

fix: bug about residual maintainInfoMap is not completely cleared

chore: optimize fix about clearing maintainInfoMap

feat: add hardhat config

chore: modify config

chore: modify config

chore: add hardhat config

feat: finish test case

chore: add readme

chore: optimize code structure

fix: bug about Repeated modified maintainingValidatorSet in loop

chore: optimize test

fix: add prettier write for test code

FIX: review comments

fix: accidentally modified code by mistake between `.sol` and `.template`

fix: bug that maintaining validators could skip the misdemeanor/felony

fix: add modification to template

chore: modify case name

chore: remove unused code

feat: add INIT_MAX_NUM_OF_MAINTAINING, INIT_MAINTAIN_SLASH_SCALE = 2;

feat: modify test for init config

fix: bug that slash msg could not be sent by BSCValidatorSet

feat: modify revert check to return

Ref: bnb-chain/BEPs#126