🐛 refresh CodeMirror editor when CSS tab is shown

[kirkkwang]

The CodeMirror editor was invisible until text was selected. Added tab show event handler to properly refresh the editor when the CSS tab becomes visible.

[github-actions]

Test Results

    3 files  ±0      3 suites  ±0   17m 50s ⏱️ -3s
2 055 tests ±0  1 999 ✅ ±0  56 💤 ±0  0 ❌ ±0 
2 082 runs  ±0  2 024 ✅ ±0  58 💤 ±0  0 ❌ ±0 

Results for commit acaaf6a. ± Comparison against base commit 984c237.

This pull request removes 42 and adds 42 tests. Note that renamed tests count towards both.

spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to destroy fcd98a7c-4fdd-443e-af0f-482d926ac286
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to edit 7b6d7b0b-009e-4ded-8df1-0274d818855f
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to read 1a5805bb-6034-473b-a132-ae017f945519
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to update 2601f71f-14bb-4d56-bf7e-ec8e4477cb64
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to destroy e651257e-d023-4850-840a-bf899164cccf
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to edit e1af1f1c-2292-4bc2-9f25-91291557b438
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to read 17c54763-bc6e-4546-b944-3f016d2c7c75
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to update 366a1f0c-39d2-40e1-8aef-28bb1ea5f20a
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor GenericWork permissions is expected not to be able to destroy 8cac715a-e694-4e72-b9b8-bd44dbc026f4
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor GenericWork permissions is expected not to be able to edit 7e441a04-b522-4e96-99ba-fc63c7e5a940
…

spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to destroy aca4d1ef-3ca4-44bb-9368-711fda365c96
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to edit 25985352-bf29-4be2-b137-5b5d439d94e9
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to read 417e98aa-9bcb-4049-af48-694bf57e98c0
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor Etd permissions is expected not to be able to update 36cd63b8-22b6-494d-9c73-1cab5a020579
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to destroy 97334dae-25ea-41d8-86a0-eedaf13611f5
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to edit a22c573d-c500-4044-b9c4-5d343143e21b
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to read 2a68ffab-941f-4cf1-9935-88985946a232
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor FileSet permissions is expected not to be able to update f05d9b7b-790d-4d1d-8325-454132dff4e1
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor GenericWork permissions is expected not to be able to destroy 2934147d-9451-4034-bbc1-e0b79e269969
spec.abilities.work_ability_spec ‑ Hyrax::Ability::WorkAbility when work depositor GenericWork permissions is expected not to be able to edit 5705c3f7-1548-41e3-b0dd-2742b96edf97
…