Add Mortar Technicals for Squad

[Endebert]

See this discussion for more information: #101

User story:

As a user, I want to be able to get accurate mortar adjustments for mortar technicals, which will be added to Squad with the V2 update. The mortar type should be selectable, and, since the ingame elevation adjustment for those mortars in shown in degrees, I also want SquadMC to display it in degrees.

Acceptance Criteria:

• mortar type can be selected in nav drawer
• elevation adjustment is shown in degrees, if mortar technical is selected as mortar type
• direction (left-right) and elevation (up-down) adjustments are easily distinguishable

Dev notes:

• calculate new mortar velocity based on table provided in the discussion (Mortars Technicals Implementation research #101) using the calcMortarSettings.js script
• functionality to select mortar type already exists for PostScriptumMC, and just needs to be ported to SquadMC: https://github.com/Endebert/squadmc/blob/dev/src/Map.vue#L557-L580
• since both direction and elevation are in degrees, UI/UX implementation could be tricky