docs[minor]: Swap gtag for supabase (#18937)

Added deps:
- `@supabase/supabase-js` - for sending inserts
- `supabase` - dev dep, for generating types via cli
- `dotenv` for loading env vars

Added script:
- `yarn gen` - will auto generate the database schema types using the
supabase CLI. Not necessary for development, but is useful. Requires
authing with the supabase CLI (will error out w/ instructions if you're
not authed).

Added functionality:
- pulls users IP address (using a free endpoint: `https://api.ipify.org`
so we can filter out abuse down the line)

TODO:
- [x] add env vars to vercel

docs/src/analytics.js

@@ -1,5 +0,0 @@
-export default function gtag(...args) {
-  if (window.gtagFeedback) {
-    window.gtagFeedback(...args);
-  }
-}

docs/src/theme/Feedback.js

@@ -1,6 +1,6 @@
 /* eslint-disable no-return-assign, react/jsx-props-no-spreading */
 import React, { useState, useEffect } from "react";
-import gtag from "../analytics";
+import { createClient } from "@supabase/supabase-js";
 
 const useCookie = () => {
   /**
@@ -90,27 +90,69 @@ function SvgThumbsDown() {
   );
 }
 
+/**
+ * Generated type for the Supabase DB schema.
+ * @typedef {import('../supabase').Database} Database
+ */
+
 const FEEDBACK_COOKIE_PREFIX = "feedbackSent";
+/** @type {Database["public"]["Enums"]["project_type"]} */
+const LANGCHAIN_PROJECT_NAME = "langchain_py_docs";
+
+/**
+ * @returns {Promise<string>}
+ */
+const getIpAddress = async () => {
+  const response = await fetch("https://api.ipify.org?format=json");
+  return (await response.json()).ip;
+};
 
 export default function Feedback() {
   const { setCookie, checkCookie } = useCookie();
   const [feedbackSent, setFeedbackSent] = useState(false);
 
-  /**
-   * @param {"good" | "bad"} feedback
-   */
-  const handleFeedback = (feedback) => {
+  /** @param {"good" | "bad"} feedback */
+  const handleFeedback = async (feedback) => {
+    if (process.env.NODE_ENV !== "production") {
+      console.log("Feedback (dev)");
+      return;
+    }
+
     const cookieName = `${FEEDBACK_COOKIE_PREFIX}_${window.location.pathname}`;
     if (checkCookie(cookieName)) {
       return;
     }
 
-    const feedbackEnv =
-      process.env.NODE_ENV === "production"
-        ? "page_feedback"
-        : "page_feedback_dev";
+    /** @type {Database} */
+    const supabase = createClient(
+      process.env.NEXT_PUBLIC_SUPABASE_URL,
+      process.env.NEXT_PUBLIC_SUPABASE_PUBLIC_KEY
+    );
+    try {
+      const ipAddress = await getIpAddress();
+
+      /**
+       * "id" and "created_at" are automatically generated by Supabase
+       * @type {Omit<Database["public"]["Tables"]["feedback"]["Row"], "id" | "created_at">}
+       */
+      const data = {
+        is_good: feedback === "good",
+        url: window.location.pathname,
+        user_ip: ipAddress,
+        project: LANGCHAIN_PROJECT_NAME,
+      };
+
+      const { error } = await supabase.from("feedback").insert(data);
+      if (error) {
+        throw error;
+      }
+    } catch (e) {
+      console.error("Failed to send feedback", {
+        e,
+      });
+      return;
+    }
 
-    gtag("event", `${feedbackEnv}_${feedback}`, {});
     // Set a cookie to prevent feedback from being sent multiple times
     setCookie(cookieName, window.location.pathname, 1);
     setFeedbackSent(true);
@@ -161,16 +203,16 @@ export default function Feedback() {
               {...defaultFields}
               role="button" // Make it recognized as an interactive element
               tabIndex={0} // Make it focusable
-              onKeyDown={(e) => {
+              onKeyDown={async (e) => {
                 // Handle keyboard interaction
                 if (e.key === "Enter" || e.key === " ") {
                   e.preventDefault();
-                  handleFeedback("good");
+                  await handleFeedback("good");
                 }
               }}
-              onClick={(e) => {
+              onClick={async (e) => {
                 e.preventDefault();
-                handleFeedback("good");
+                await handleFeedback("good");
               }}
             >
               <SvgThumbsUp />
@@ -179,16 +221,16 @@ export default function Feedback() {
               {...defaultFields}
               role="button" // Make it recognized as an interactive element
               tabIndex={0} // Make it focusable
-              onKeyDown={(e) => {
+              onKeyDown={async (e) => {
                 // Handle keyboard interaction
                 if (e.key === "Enter" || e.key === " ") {
                   e.preventDefault();
-                  handleFeedback("bad");
+                  await handleFeedback("bad");
                 }
               }}
-              onClick={(e) => {
+              onClick={async (e) => {
                 e.preventDefault();
-                handleFeedback("bad");
+                await handleFeedback("bad");
               }}
             >
               <SvgThumbsDown />