[Feature] Incident Details Modal

[giranm]

Summary

This PR closes #144 which provides a dedicated incident details page for PagerDuty Live.

THIS IS CURRENTLY BEING WORKED ON AS A DRAFT

TODO

• Create onClick handler and redux framework that toggles IncidentDetailsModalComponent when an incident row is selected/clicked in the main table.
• Ensure that the store for reducer incidentDetails is updated with the "currentIncident" to be viewed (upon above action)
• Update IncidentDetailsModalComponent to display data from incidentDetails.incident
• Update SettingsModal to account for customisation of the alerts table (will require similar redux plumbing)
• Create src/redux/alerts_table which mimics interactivity of src/redux/incident_table (e.g. store alerts table layout)
• Update AlertsTableComponent to mimic IncidentTableComponent, except pointing to the alerts redux plumbing
• Update styling via SCSS and custom classNames for friendly UI/UX
• Add i18n & react-i18next translation tokens as required
• (Optional) Add alert specific actions to AlertsTableComponent