Modifications to humanoid model.

- Increased hip flexion maximum.
- Symmetrised shoulder and ankle joints.
- Added hamstring tendons which couple the hip and knee at large flexion values.
- Moved duplicated values into defaults.
- Added two keyframes.
- Improved lighting.
- Changed naming convention.
- Moved description into README.md

PiperOrigin-RevId: 473745371
Change-Id: I95bf915c4caf3d5cf06c325cd73284d78a3d836e

doc/changelog.rst

@@ -3,6 +3,19 @@ Changelog
 =========
 
 
+Upcoming version (not yet released)
+-----------------------------------
+
+General
+^^^^^^^
+
+- Updates to humanoid model:
+
+   - Added two keyframes (stand-on-one-leg and squat).
+   - Increased maximum hip flexion angle.
+   - Added hamstring tendons which couple the hip and knee at high hip flexion angles.
+   - General cosmetic improvements, including improved use of defaults and better naming scheme.
+
 Version 2.2.2 (September 7, 2022)
 ---------------------------------