fix: wrap Node.js API call in environment check

- process.env is not available in browser environments
- Wrap process.env call in main.ts in if statement that checks for browser presence

Author: seansica

src/main.ts

@@ -2,31 +2,31 @@ import axios from 'axios';
 import { v4 as uuidv4 } from 'uuid';
 
 import {
-  type StixBundle,
-  type AttackObject,
   extensibleStixBundleSchema,
+  type AttackObject,
   type AttackObjects,
+  type StixBundle,
 } from './schemas/sdo/stix-bundle.schema.js';
 
 import {
-  techniqueSchema,
-  tacticSchema,
-  matrixSchema,
-  mitigationSchema,
-  relationshipSchema,
-  dataSourceSchema,
+  analyticSchema,
+  assetSchema,
+  campaignSchema,
+  collectionSchema,
   dataComponentSchema,
+  dataSourceSchema,
+  detectionStrategySchema,
   groupSchema,
-  malwareSchema,
-  toolSchema,
-  markingDefinitionSchema,
   identitySchema,
-  collectionSchema,
-  campaignSchema,
-  assetSchema,
   logSourceSchema,
-  detectionStrategySchema,
-  analyticSchema,
+  malwareSchema,
+  markingDefinitionSchema,
+  matrixSchema,
+  mitigationSchema,
+  relationshipSchema,
+  tacticSchema,
+  techniqueSchema,
+  toolSchema,
 } from './schemas/index.js';
 
 import {
@@ -53,9 +53,11 @@ const readFile = async (path: string): Promise<string> => {
   }
 };
 
-const GITHUB_BASE_URL =
-  process.env.GITHUB_BASE_URL ||
-  'https://raw.githubusercontent.com/mitre-attack/attack-stix-data/master';
+let GITHUB_BASE_URL = ""
+if (typeof window !== 'undefined') {
+  GITHUB_BASE_URL =
+    process.env.GITHUB_BASE_URL || 'https://raw.githubusercontent.com/mitre-attack/attack-stix-data/master';
+}
 
 interface DataSourceMap {
   [key: string]: {