fix(docs): final updates before 0.26.1

- Indicate where xtask looks for wasi-sdk
- Indicate where `build --wasm` looks for and downloads wasi-sdk binary
  to
- Mark native runtime as experimental, describe limitations
- Note ABI 13 support limitations
- Mention that `test --wasm` and `parse --wasm` require
  `--features=wasm` build

docs/src/cli/test.md

@@ -55,7 +55,7 @@ The graphs are constructed with [graphviz dot][dot], and the output is written t
 
 ### `--wasm`
 
-Compile and run the parser as a Wasm module.
+Compile and run the parser as a Wasm module (only if the tree-sitter CLI was built with `--features=wasm`).
 
 ### `--open-log`