Extend uavcan si angle and length types (#150)

In certain applications, the `float32` representation in the `si` types
can be unnecessarily wide. To address this, I propose introducing a
`Narrow` variant, analogous to the existing `Wide` variant.

Additionally, it would be beneficial to have a standardized `Vector3`
type for angles.

This PR introduces the following extensions to uavcan.si:
* A new `Vector3` type for representing angles.
* `Narrow` and `Wide` variations for selected angle and length types.

Author: ycherniavskyi

uavcan/si/sample/angle/NarrowScalar.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float16 radian
+@sealed

uavcan/si/sample/angle/NarrowVector3.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float16[3] radian
+@sealed

uavcan/si/sample/angle/Vector3.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float32[3] radian
+@sealed

uavcan/si/sample/angle/WideScalar.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float64 radian
+@sealed

uavcan/si/sample/angle/WideVector3.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float64[3] radian
+@sealed

uavcan/si/sample/length/NarrowScalar.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float16 meter
+@sealed

uavcan/si/sample/length/NarrowVector3.1.0.dsdl

@@ -0,0 +1,3 @@
+uavcan.time.SynchronizedTimestamp.1.0 timestamp
+float16[3] meter
+@sealed

uavcan/si/unit/angle/NarrowScalar.1.0.dsdl

@@ -0,0 +1,2 @@
+float16 radian
+@sealed

uavcan/si/unit/angle/NarrowVector3.1.0.dsdl

@@ -0,0 +1,2 @@
+float16[3] radian
+@sealed

uavcan/si/unit/angle/Vector3.1.0.dsdl

@@ -0,0 +1,2 @@
+float32[3] radian
+@sealed