Changed 'verifyNum' to return a BigInt.

[Randy808]

To run locally, npm install and use the following snippets:

# Bitcoin
export API_URL=https://blockstream.info/api
export PORT=4999
source flavors/blockstream/config.env
source flavors/bitcoin-mainnet/config.env
npm run dev-server

# Liquid
export API_URL=https://blockstream.info/liquid/api
export PORT=5000
source flavors/blockstream/config.env
source flavors/liquid-mainnet/config.env
npm run dev-server

---

To test:

• Download wallycore.js and wallycore.wasm located at https://blockstream.info/liquid/libwally/wallycore.js and https://blockstream.info/liquid/libwally/wallycore.wasm respectively
• Make a folder called libwally in client/src/lib/ and place the 2 downloaded files in there
• Add the following lines to dev-server.js after the line router.get('/app.js', browserify(rpath('client/src/run-browser.js'))):

router.get('/libwally/wallycore.js', (req, res) => res.sendFile(rpath('client/src/lib/libwally/wallycore.js')))
router.get('/libwally/wallycore.wasm', (req, res) => res.sendFile(rpath('client/src/lib/libwally/wallycore.wasm')))

• Start the dev server and navigate to a url that unblinds a value that requires more than 53 bits