feat: transition matrices for model diagram

[shawnyama]

Description

• created tera-tooltip component
• tooltip can appear within a specified position relative to the div it is wrapped around
• Stratified transition matrices appear when you click on them in the model diagram
• tera-stratified-matrix-preview.vue houses a preview of what the transition matrix looks like, this is what's put inside the tera-tooltip slot

UX thoughts

• I have to click the unlock to adjust button for the transition hovering to work. That pointer-events: none rule for when the diagram is locked might be too much. I think just disabling the zoom may be good enough.
• When I click on a node all the other ones turn a little transparent, I don't think there is a need for this since model editing isn't done in the diagram anymore.

Screen.Recording.2024-04-16.at.11.16.52.AM.mov

To do later

The design has these colourful borders based on which strata the cells belong to, thought I'd save that for later.

[YohannParis]

Well done!