Alternative Token Cover

This module provides options to calculate how much cover a targeted token has, with respect to a viewer token. Various options are provided to modify how the cover calculation is made. The GM can also define low, medium, and high levels of cover, and associate each level of cover with an active effect that is applied to the targeted token when it has cover. Workflow options are provided to facilitate automation.

This module is closely related to [Alternative Token Visibility](https://github.com/caewok/fvtt-token-visibility). Both rely on the same underlying algorithms to determine whether there are obstacles between the viewer and the target.

Cover Algorithm choices:
- Points. Test whether a 3d ray from a point on the viewer token to a point on the target token is blocked by an obstacle. Multiple points on the target can be tested to determine whether a threshold percentage of rays is met for cover. For overhead tiles, considers them to block unless the ray passes through a transparent portion of the tile.
- Area2d. Test the percentage of the overhead view of a target token that is viewable from the perspective of a point on the viewer token. For overhead tiles, does not consider transparency.
- Area3d. Test the percentage of the 3d view of a target token that is viewable from the perspective of a point on the viewer token. For overhead tiles, uses webGL to test transparency.

Major features:
- Choose whether one or more points on the viewing target are tested for cover, with the best result taken. Options include a "stereo" version that uses two points on the front facing side of the token.
- Adjust viewer and target point locations, shifting from the token border to the center.
- Account for wall height (using the [Wall Height](https://github.com/theripper93/wall-height) module) and overhead tiles.
- Adjust the vision height for tokens and prone tokens.

## Dependencies
- [libWrapper](https://github.com/ruipin/fvtt-lib-wrapper)
- [socketlib](https://github.com/manuelVo/foundryvtt-socketlib)

## Recommended module additions
- [Alternative Token Visibility](https://github.com/caewok/fvtt-token-visibility). Needed if you want token vision to exactly match token cover.
- [Wall Height](https://github.com/theripper93/wall-height). Not only does Wall Height provide the ability to set elevation for wall tops and bottoms, it also gives tokens height based on their size. The Area3d option for Alt Token Visibility takes full advantage of token height.
- [Elevated Vision](https://github.com/caewok/fvtt-elevated-vision). Can assist with setting terrain and token elevations.
- [Midiqol](https://gitlab.com/tposney/midi-qol). If midiqol is installed, additional options are presented to allow cover calculations during an attack roll.