feat: add angle units and formula documentation

lib/formulas.d4rt

@@ -2,6 +2,16 @@
   // Free fall distance (vertical)
   {
     name: "Free Fall Distance",
+    description: '''
+Calculates vertical displacement under constant gravity
+
+`h = ½gt²`
+
+Where:
+- `g` = Gravitational acceleration (9.81 m/s² on Earth)
+- `t` = Time in free fall (seconds)
+
+![Free Fall Diagram](https://upload.wikimedia.org/wikipedia/commons/thumb/7/72/Free-fall.svg/1200px-Free-fall.svg.png)''',
     input: [
       {name: "t", magnitude: "s"},  // Time in seconds
       {name: "g", magnitude: "m/s²"}  // Gravitational acceleration
@@ -13,6 +23,17 @@
   // Newton's Law of Universal Gravitation
   {
     name: "Gravitational Force",
+    description: '''
+Newton's law of universal gravitation
+
+`F = G(m₁m₂)/r²`
+
+Where:
+- `G` = Gravitational constant (6.674×10⁻¹¹ N·m²/kg²)
+- `m₁`, `m₂` = Masses of two objects
+- `r` = Distance between centers of masses
+
+![Gravitation](https://upload.wikimedia.org/wikipedia/commons/thumb/3/33/NewtonsLawOfUniversalGravitation.svg/1200px-NewtonsLawOfUniversalGravitation.svg.png)''',
     input: [
       {name: "m1", magnitude: "kg"},  // Mass 1
       {name: "m2", magnitude: "kg"},  // Mass 2
@@ -25,6 +46,16 @@
   // Kinetic Energy
   {
     name: "Kinetic Energy",
+    description: '''
+Energy possessed by a moving object
+
+`KE = ½mv²`
+
+Where:
+- `m` = Mass of object
+- `v` = Velocity of object
+
+![Kinetic Energy](https://upload.wikimedia.org/wikipedia/commons/thumb/4/44/Kinetic_energy.svg/1200px-Kinetic_energy.svg.png)''',
     input: [
       {name: "m", magnitude: "kg"},  // Mass
       {name: "v", magnitude: "m/s"}  // Velocity
@@ -36,6 +67,13 @@
   // Projectile Motion Range
   {
     name: "Projectile Range",
+    description: "Calculates horizontal distance of projectile motion\n\n"
+                 "`R = (v² sin(2θ))/g`\n\n"
+                 "Where:\n"
+                 "- `v` = Initial velocity\n"
+                 "- `θ` = Launch angle\n"
+                 "- `g` = Gravitational acceleration\n\n"
+                 "![Projectile Motion](https://upload.wikimedia.org/wikipedia/commons/thumb/5/52/Projectile_motion_diagram.png/800px-Projectile_motion_diagram.png)",
     input: [
       {name: "v", magnitude: "m/s"},  // Initial velocity
       {name: "θ", magnitude: "deg"}   // Launch angle

lib/main.dart

@@ -33,7 +33,8 @@ Future<UnitCorpus> createTestCorpus() async {
     "lib/units/pressure.d4rt.units",
     "lib/units/temperature.d4rt.units",
     "lib/units/velocity.d4rt.units",
-    "lib/units/mass.d4rt.units"
+    "lib/units/mass.d4rt.units",
+    "lib/units/angle.d4rt.units"
   ];
   
   for (final resourcePath in resources) {

lib/units/angle.d4rt.units

@@ -0,0 +1,12 @@
+[
+  {"name": "radian", "symbol": "rad", "isBase": true},
+  {"name": "degree", "symbol": "°", "baseUnit": "radian", "factor": 0.017453292519943295},
+  {"name": "gradian", "symbol": "gon", "baseUnit": "radian", "factor": 0.015707963267948967},
+  {"name": "revolution", "symbol": "rev", "baseUnit": "radian", "factor": 6.283185307179586},
+  {"name": "arcminute", "symbol": "'", "baseUnit": "radian", "factor": 0.0002908882086657216},
+  {"name": "arcsecond", "symbol": "\"", "baseUnit": "radian", "factor": 0.00000484813681109536},
+  {"name": "binary degree", "symbol": "brad", "baseUnit": "radian", "factor": 0.02454369260617026},
+  {"name": "quadrant", "symbol": "quad", "baseUnit": "radian", "factor": 1.5707963267948966},
+  {"name": "sextant", "symbol": "sextant", "baseUnit": "radian", "factor": 1.0471975511965976},
+  {"name": "octant", "symbol": "octant", "baseUnit": "radian", "factor": 0.7853981633974483}
+]