fix: Ketcher2 iframe: load molfile when editor ready

[haditariq]

This PR resolves Issue # 159:

• Ketcher2 fails to load content while switching between ketcher 1 and ketcher 2
• Resolved with event Listener
• Demo available https://github.com/ComPlat/chemotion_ELN/assets/25753582/54ef45e4-0681-40ec-ae3d-36cd67dc043a

[github-actions[bot]]

LCOV of commit 8f3091e during Continuous Integration #3016

Summary coverage rate:
  lines......: 64.2% (13682 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a

[github-actions[bot]]

LCOV of commit 6d5e864 during Continuous Integration #3063

Summary coverage rate:
  lines......: 64.2% (13684 of 21318 lines)
  functions..: no data found
  branches...: no data found

Files changed coverage rate: n/a