docs/api.md documents props as `PropTypes`, and several entries are wrong

Start with docs/api.md and audit its four prop tables against the TypeScript declarations and the LiveProvider transformCode call site. Update the documented types and defaults, correct the transformCode return type, and account for LiveEditor’s Partial surface. A changeset is needed for the published declaration change.

docs/api.md types every prop as PropTypes.string, PropTypes.bool, and so on — 16 rows
across four tables. There is no prop-types dependency in the repo. The props are
TypeScript, so the notation describes runtime validation that does not happen.

The file is already inconsistent with itself: the withLive() table types element as
React.Element, which is not a real type either (React.ReactElement).

Auditing the tables to convert them turned up three entries that are wrong on the facts, not
just the notation.

language default is documented as jsx

| language | `PropTypes.string` | ... (Default: `jsx`) |

LiveProvider defaults it to tsx:

language = "tsx",

LivePreview's Component is not a node

Documented as PropTypes.node. It is React.ElementType — a tag name or component, not
rendered output. node would be the wrong choice even in PropTypes terms (elementType).

transformCode's declared type contradicts its own call site

The docs say "accepts and returns the code to be transpiled", which matches what
LiveProvider actually does:

const transformResult = transformCode ? transformCode(newCode) : newCode;
const transformedCode = await Promise.resolve(transformResult);
if (typeof transformedCode !== "string") {
  throw new Error("Code failed to transform");
}

The type says the return value is discarded:

transformCode?(code: string): void;

Here the docs are right and the source is wrong. TypeScript permits returning a value where
void is expected, so callers are not broken — but anyone reading the declarations sees a
mutator. Should be string | Promise<string>.

Order

1. Fix transformCode's return type. Separate from the docs work: it ships in the published
   declarations and needs a changeset.
2. Convert the four tables to TypeScript types, correcting language, Component, and
   element along the way.
3. While in there, LiveEditor takes Partial<EditorProps>, so the three documented props
   are not its whole surface.