chore: fix linting

Fixes linting issues in master:

```console
% npm run lint

> node-datachannel@0.24.0 lint
> eslint . --ext .ts --ext .mts

/path/to/murat-dogan/node-datachannel/src/lib/node-datachannel.ts
  1:5   error  'nodeDataChannel' is never reassigned. Use 'const' instead  prefer-const
  1:23  error  Require statement not part of import statement              @typescript-eslint/no-var-requires
```

Author: achingbrain

src/lib/node-datachannel.ts

@@ -1,2 +1,3 @@
-let nodeDataChannel = require('../../build/Release/node_datachannel.node');
+// @ts-expect-error no types
+import nodeDataChannel = require('../../build/Release/node_datachannel.node');
 export default nodeDataChannel;