Feat remove ied duplicates issue

[stee-re]

Resolves #121

Summary

When multiple IEDs reference the same LNode, removing those IEDs sequentially can result in duplicate LNode
entries with iedName="None". This PR adds an option to detect and remove such duplicates instead of
creating redundant entries, by default. Callers can use the options to prevent this happening:

remove(myIEDElement, {removeLNodes: false});

Changes

• tIED/removeIED.ts:
  • Added RemoveIedOptions interface with a removeLNodes flag (defaults to true)
  • Introduced a lNodeKey() helper to compute a unique key per LNode
  • When removeLNodes is true (default), duplicate LNodes already set to "None" are removed rather
    than duplicated
  • When removeLNodes is false, LNodes are only updated to "None" (previous behaviour)
• index.ts: Exported RemoveIedOptions type
• tIED/removeIED.spec.ts: Added tests for duplicate removal and opt-out behaviour
• tIED/removeIED.testfile.ts: Added test fixture with duplicate LNode scenario
• .gitignore: Added IDE and build artifact patterns