Update Wasm README (open-policy-agent#5303)

Signed-off-by: Anders Eknert <[email protected]>

Co-authored-by: Stephan Renatus <[email protected]>

Author: anderseknert

wasm/README.md

@@ -1,26 +1,30 @@
 # OPA-WASM
 
 This directory contains a library that implements various low-level
-operations for policies compiled into WebAssembly (WASM). Specifically, the
-library implements:
-
-* JSON parsing
-* JSON AST (e.g., comparison, iteration, lookup, etc.)
-* String operations
-* Memory allocation
+operations for policies compiled into WebAssembly (Wasm). Specifically, the
+library implements most of the built-in functions provided by OPA. See the "Wasm"
+tag next to each function listed in the
+[built-in function reference](https://www.openpolicyagent.org/docs/latest/policy-reference/#built-in-functions)
+for the complete list, or the 
+[builtin_metadata.json](https://github.com/open-policy-agent/opa/blob/main/builtin_metadata.json) file for programmatic purposes.
 
 This library does not make any backwards compatibility guarantees.
 
+## Documentation
+
+See the [OPA docs](https://www.openpolicyagent.org/docs/latest/wasm/) on Wasm for an overview of the integration,
+compilation options, and more.
+
 ## Development
 
 You should have Docker installed to build and test changes to the library. We
-commit the output of the build (`opa.wasm`) into the repository so it's
+commit the output of the build (`opa.wasm`) into the repository, so it's
 important for the build output to be reproducible.
 
 You can build the library by running `make build`. This will produce WASM
 executables under the `_obj` directory.
 
-You can test the library by running `make test`. By default the test runner
+You can test the library by running `make test`. By default, the test runner
 does not print messages when tests pass. If you run `make test VERBOSE=1` it
 will log all of the tests that were run.
 
@@ -44,4 +48,4 @@ target will:
 
 1. Build the OPA-WASM library
 2. Copy the library into the [internal/compiler/wasm/opa](../internal/compiler/wasm/opa) directory.
-3. Run the tool to generate the [internal/compiler/wasm/opa/opa.go](../internal/compiler/wasm/opa/opa.go) file.
+3. Run the tool to generate the [internal/compiler/wasm/opa/opa.go](../internal/compiler/wasm/opa/opa.go) file.