Revise payment tutorials, add/remove screenshots

_code-samples/modular-tutorials/five-bells.js

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+const cc = require('five-bells-condition');
+const crypto = require('crypto');
+
+// 1. Generate a random 32-byte seed
+const preimageData = crypto.randomBytes(32);
+
+// 2. Create a PreimageSha256 fulfillment object
+const fulfillment = new cc.PreimageSha256();
+
+// 3. Set the preimage
+fulfillment.setPreimage(preimageData);
+
+// 4. Generate the condition (binary)
+const conditionBinary = fulfillment.getConditionBinary();
+
+// 5. Generate the fulfillment (binary)
+const fulfillmentBinary = fulfillment.serializeBinary();
+
+// Convert to hex for easier use
+const conditionHex = conditionBinary.toString('hex').toUpperCase();
+const fulfillmentHex = fulfillmentBinary.toString('hex').toUpperCase();
+
+console.log('Condition (hex):', conditionHex);
+console.log('Fulfillment (hex):', fulfillmentHex);