fix: include sparkplug proto in build

this isn't the ideal way to include the proto definition, but the build system for this project is too convoluted for my smooth brain to understand

Author: ferm10n

backend/src/Model/sparkplugb.ts

@@ -2,9 +2,9 @@ import { readFileSync } from 'fs'
 import * as protobuf from 'protobufjs'
 import { Base64Message } from './Base64Message'
 import { Decoder } from './Decoder'
+import { protobufStr } from './sparkplugb_proto'
 
-const buffer = readFileSync(require.resolve('../../../../res/sparkplug_b.proto'))
-const root = protobuf.parse(buffer.toString()).root
+const root = protobuf.parse(protobufStr).root
 export let SparkplugPayload = root.lookupType('com.cirruslink.sparkplug.protobuf.Payload')
 
 export const SparkplugDecoder = {

res/sparkplug_b.proto renamed to backend/src/Model/sparkplugb_proto.ts

@@ -1,3 +1,4 @@
+export const protobufStr = `
 syntax = "proto2";
 
 //
@@ -195,3 +196,4 @@ message Payload {
     optional bytes    body          = 5;        // To optionally bypass the whole definition above
     extensions                      6 to max;   // For third party extensions
 }
+`