add toString() in Document's ctor to prevent unreadable error message

[zombieyang]

if I read some text from file by fs, sometime I will forget to pass 'utf-8' as arguments and get a Buffer.
And if I use this content to create a vectorStore, I will get a unreadable error message

const content = readFileSync(join(__dirname, 'input.txt'))  // should be readFileSync(join(__dirname, 'input.txt'), 'utf-8')
Chroma.fromTexts(
        [content],
        [{}],
        embeddingModel,
        {
            collectionName: "abc",
        }
    );


// will got this error
TypeError: t.replaceAll is not a function
    at file:///T:/_CODE_/langchain-test2/node_modules/langchain/dist/embeddings/openai.js:68:79
    at Array.map (<anonymous>)
    at OpenAIEmbeddings.embedDocuments (file:///T:/_CODE_/langchain-test2/node_modules/langchain/dist/embeddings/openai.js:68:66)
    at Chroma.addDocuments (file:///T:/_CODE_/langchain-test2/node_modules/langchain/dist/vectorstores/chroma.js:39:53)
    at Chroma.fromDocuments (file:///T:/_CODE_/langchain-test2/node_modules/langchain/dist/vectorstores/chroma.js:120:24)
    at Chroma.fromTexts (file:///T:/_CODE_/langchain-test2/node_modules/langchain/dist/vectorstores/chroma.js:116:23)
    at insertIntoChroma (file:///T:/_CODE_/langchain-test2/chroma.mjs:57:18)
    at run (file:///T:/_CODE_/langchain-test2/chroma.mjs:47:19)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

That is because langchain try to invoke replaceAll for the inputting Buffer.

---

This PR add a toString() invoke when creating a vectorstore by text. I don't know whether should we check the typeof text or use toString directly. If you think it is better to check the type and throw Error, plz let me know.

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[nfcampos]

Thanks for this @zombieyang can we do this instead in https://github.com/hwchase17/langchainjs/blob/main/langchain/src/document.ts#L23

[zombieyang]

Oh, that's way better. Thank you.
I force pushed my new commit.

[nfcampos]

Great, thank you!

[jacobcwright]

This issue still occurs if not on Node 16+

[zombieyang]

This issue still occurs if not on Node 16+

langchain.js declared a node version limitation in package.json.
https://github.com/hwchase17/langchainjs/blob/main/langchain/package.json#L7

I even cannot run any http request in node16. How can you run that?