Add secrets creation option for workspace creation

[paulovmr]

Introduce a new expandable section on the Properties step in the Workspace creation wizard, very similar to the volumes one, using the same components, to add and list secrets.

Each secret will contain these fields:

• Name: Text input.
• Mount Path: Text input.
• Default Mode: Text input.

[paulovmr]

/assign
/area frontend
/area v2

[paulovmr]

This is the initial frontend task for #239
Next we can introduce search and a new screen for secrets management.

[thaorell]

Could this be assigned to me :D ?

[paulovmr]

/assign @thaorell