Update fee-paying-related code in examples

[homura]

The hard-code code about fee-paying examples should be revised to use payFeeByFeeRate to calculate transaction fee instead of using a fixed value of 0.001 CKB

lumos/examples/pw-lock-metamask/lib.ts

Lines 59 to 62 in ccd8213

	// additional 0.001 ckb for tx fee
	// the tx fee could calculated by tx size
	// this is just a simple example
	const neededCapacity = BI.from(options.amount).add(100000);