add to MVP-JS.md and spec docs

proposals/gc/MVP-JS.md

@@ -63,3 +63,16 @@ internal reference value that is being externalized:
  - If the value is a struct or array reference, create a new JS wrapper for it.
  - Otherwise if the reference is an internalized host reference, return the
    original external host reference.
+
+## Implementation-defined Limits
+
+The following limits will be added to the Implementation-defined Limits
+[section](https://webassembly.github.io/spec/js-api/index.html#limits) of the JS
+API.
+
+ - The maximum number of recursion groups is 1000000. (The maximum number of
+   individual types remains unchanged and is also 1000000.)
+ - The maximum number of struct fields is 10000.
+ - The maximum number of operands to `array.new_fixed` is 10000.
+ - The maximum length of a supertype chain is 63. (A type declared with no
+   supertypes has a supertype chain of length 0)

proposals/gc/MVP.md

@@ -108,7 +108,7 @@ New abbreviations are introduced for reference types in binary and text format,
   - `module ::= {..., types vec(<deftype>)}`
   - a `rec` definition defines a group of mutually recursive types that can refer to each other; it thereby defines several type indices at a time
   - a single type definition, as in Wasm before this proposal, is reinterpreted as a short-hand for a recursive group containing just one type
-  - Note that the number of type section entries is now the number of recursion groups rather than the number of individual types. 
+  - Note that the number of type section entries is now the number of recursion groups rather than the number of individual types.
 
 * `subtype` is a new category of type defining a single type, as a subtype of possible other types
   - `subtype ::= sub final? <typeidx>* <strtype>`
@@ -779,9 +779,10 @@ The opcode for heap types is encoded as an `s33`.
 | 0xfb70 | `extern.internalize` | |
 | 0xfb71 | `extern.externalize` | |
 
+
 ## JS API
 
-See [GC JS API document](../../document/js-api/index.bs).
+See [GC JS API document](MVP-JS.md).
 
 ## Questions