Fix documentation (#215)

* Remove HTML line breaks from Unity Academy

* Use lists for documentation

* Use markdown bold syntax instead of HTML

* Reformat remaining items in Unity Academy

* Remove extraneous HTML line breaks

Partially cleans up Physics module documentation.

* Reformat Physics 2D documentation

* Fix Unity Academy functions documentation

src/bundles/physics_2d/index.ts

@@ -1,31 +1,27 @@
 /**
  * 2D Phyiscs simulation module for Source Academy.
  *
- * A <b>vector</b> is defined by its coordinates (x and y). The 2D vector is used to
+ * A **vector** is defined by its coordinates (x and y). The 2D vector is used to
  * represent direction, size, position, velocity and other physical attributes in
  * the physics world. Vector manipulation and transformations between vector and array
  * types are supported.
  *
- * <br>
- *
- * A <b>force</b> is defined by its direction (a vector), its magnitude, duration and
+ * A **force** is defined by its direction (a vector), its magnitude, duration and
  * start time. A force is only actively applied if:
+ *
  * ```
  * diff > 0 && diff < duration, where diff is world time - start time
  * ```
  *
- * <br>
- *
- * A <b>world</b> is the single physics world the module is based on.
+ * A **world** is the single physics world the module is based on.
  *
  * - `set_gravity` needs to be called once at the start of the program to initialize the world
  * and set the gravity.
  * - `make_ground` and `add_wall` are optional but recommended to be used to set boundaries
  * in the world.
  *
- * <br>
+ * An **object** is initially defined in the add function by:
  *
- * An <b>object</b> is initially defined in the add function by:
  * - shape: which add function was used (e.g. `add_box_object`)
  * - position: initial position
  * - velocity: initial velocity
@@ -34,27 +30,27 @@
  * - isStatic (whether it is affected by physics)
  *
  * There are also additional attributes that can be set after an object has been added:
+ *
  * - density: mass per area of object
  * - friction: how much friction the object surface has
  *
  * There are two ways to apply a force on a given object:
+ *
  * - `apply_force`: applies a force to an object at a given object
  * - `apply_force_to_center`: applies a force to an object directly at its center
  *
  * Detection of collision and precise starting time are provided by:
+ *
  * - `is_touching`
  * - `impact_start_time`
  *
- * <br>
- *
  * After adding objects to the world, calling `update_world` will simulate the world.\
  * The suggested time step is 1/60 (seconds).
  *
  * Visualization of the physics world can also be seen in the display tab.
 *
- * <br>
- *
  * The following example simulates a free fall of a circle object.
+ *
  * ```
  * import { set_gravity, make_vector, add_circle_object, update_world } from "physics_2d";
  *
@@ -71,7 +67,6 @@
  * update_world(1/60);
  * }
  * ```
- * <br>
  *
  * @module physics_2d
  * @author Muhammad Fikri Bin Abdul Kalam