[Docs] Update TS installation docs to use pnpm exec instead of depr…

…ecated `pnpx` (#1144)

[`pnpx` has been deprecated](pnpm/pnpm#3652) in
favor of `pnpm exec` and `pnpm dlx`.

This PR modifies the installation docs for Typescript / pnpm to use
`pnpm exec` instead of `pnpx`. `exec` is favored over `dlx` in this
instance since the `baml-cli` command is installed in the local
`node_modules/.bin`.
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----

> [!IMPORTANT]
> Update TypeScript installation docs to use `pnpm exec` instead of
deprecated `pnpx`.
> 
>   - **Documentation**:
> - Update `typescript.mdx` to use `pnpm exec baml-cli init` instead of
deprecated `pnpx baml-cli init`.
> 
> <sup>This description was created by </sup>[<img alt="Ellipsis"
src="https://img.shields.io/badge/Ellipsis-blue?color=175173">](https://www.ellipsis.dev?ref=BoundaryML%2Fbaml&utm_source=github&utm_medium=referral)<sup>
for 41c0fb9. It will automatically
update as commits are pushed.</sup>

<!-- ELLIPSIS_HIDDEN -->

Co-authored-by: hellovai <[email protected]>

fern/01-guide/02-languages/typescript.mdx

@@ -38,7 +38,7 @@ To set up BAML with Typescript do the following:
         ```
 
         ```bash pnpm
-        pnpx baml-cli init
+        pnpm exec baml-cli init
         ```
 
         ```bash yarn
@@ -120,4 +120,4 @@ To set up BAML with Typescript do the following:
 
     ```
     </CodeBlocks>
-</Steps>
+</Steps>