web build did not like fs import at top of src/files/deno. Conditiona…

…lly load library. Maybe better off just attempting text call and seeing if it errors out.

bids-validator/src/files/deno.ts

@@ -2,7 +2,6 @@
  * Deno specific implementation for reading files
  */
 import { basename, join } from '@std/path'
-import { existsSync } from '@std/fs'
 import * as posix from '@std/path/posix'
 import { type BIDSFile, FileTree } from '../types/filetree.ts'
 import { requestReadPermission } from '../setup/requestPermissions.ts'
@@ -150,13 +149,16 @@ async function _readFileTree(
  */
 export async function readFileTree(rootPath: string): Promise<FileTree> {
   const ignore = new FileIgnoreRules([])
-  if (existsSync(join(rootPath, '.bidsignore'))) {
-        const ignoreFile = new BIDSFileDeno(
-          rootPath,
-          '.bidsignore',
-          ignore,
-        )
-        ignore.add(await readBidsIgnore(ignoreFile))
+  if (globalThis.Deno) {
+    import { existsSync } from '@std/fs'
+    if (existsSync(join(rootPath, '.bidsignore'))) {
+          const ignoreFile = new BIDSFileDeno(
+            rootPath,
+            '.bidsignore',
+            ignore,
+          )
+          ignore.add(await readBidsIgnore(ignoreFile))
+    }
   }
   return _readFileTree(rootPath, '/', ignore)
 }