Add aliases for MjModel loading functions and expose string constants as properties.

Introduces `from_xml_path` and `from_binary_path` as more idiomatic aliases for `mj_loadXML` and `mj_loadModel` respectively. Refactors the binding of `mj*STRING` constants. Instead of exposing `get_mj*STRING` functions, these constants are now available as properties on the `Module` object. Runtime getters are added via EM_ASM to lazily call the underlying C++ functions.

PiperOrigin-RevId: 882566011
Change-Id: Id3bd5c23704fd122af30a50aed089bd3143fbc96

wasm/README.md

@@ -348,23 +348,31 @@ mujoco.mjtDisableBit.mjDSBL_CLAMPCTRL.value
 ```
 
 ### Constants
-Scalar constants will be accessed the same way they are on python, simply:
+Scalar constants can be accessed as properties:
 
 ```javascript
 mujoco.mjNEQDATA
 ```
 
-Due to Embind limitations, more complex constants that are not scalar, but are
-represented in more dimensions are exposed as functions. E.g. to use
-`mujoco.mjFRAMESTRING` you will need to call a function:
+Non-scalar constants like `mjFRAMESTRING` are also accessed as properties, and
+return JavaScript arrays:
 
 ```javascript
-mujoco.get_mjFRAMESTRING()
+mujoco.mjFRAMESTRING
 ```
 
 This will return a javascript array representation of the values in MuJoCo
 `mjFRAMESTRING`.
 
+> [!NOTE]
+> You will notice constants like `mjFRAMESTRING` are typed as `any`. This is
+> because they are bound using `emscripten::val::array()` in C++, and Embind
+> maps `emscripten::val` to `any` in TypeScript definition files. While
+> `EMSCRIPTEN_DECLARE_VAL_TYPE(StringArray)` could be used to define
+> `StringArray` as an alias for `emscripten::val` and hint to Embind how to
+> handle conversions in function signatures or when using `.as()` it does not
+> change how `emscripten::constant` infers types for properties.
+
 ## Development
 
 In order to change the bindings you will need to change the [`bindings.cc`](codegen/generated/bindings.cc)