enhance: add doc for Internet search tools

docs/docs/tools/internet-search.md

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+# Internet Search
+
+## Overview
+
+There are a few different Internet search tools for GPTScript:
+
+- `bing`
+- `bing-image`
+- `brave`
+- `brave-image`
+- `duckduckgo`
+- `google`
+- `google-image`
+
+Each of these tools use the corresponding search engine's API to perform searches and return results that
+the LLM can process. The number of results returned will depend on the
+search engine. This is the format of the results:
+
+Web search format:
+```
+Title: the title of the web page
+URL: the link to the web page
+Description: a short snippet from the web page
+
+Title: ...
+URL: ...
+Description: ...
+
+<etc.>
+```
+
+Image search format:
+```
+Title: the title of the image
+Source: the link to the web page where the image came from
+Image URL: the link to the image
+
+Title: ...
+Source: ...
+Image URL: ...
+
+<etc.>
+```
+
+The tools are developed in the [gptscript-ai/search repo](https://github.com/gptscript-ai/search).
+
+## Setup
+
+:::note
+This will become easier in the future, once packaging for remote GPTScript tools has been implemented.
+:::
+
+To set up your local environment to use these tools, do the following:
+
+```bash
+# Clone the repo
+git clone https://github.com/gptscript-ai/search.git
+
+# Build the Go binary
+make build
+```
+
+Now you can reference the search tools by the relative path to the `tool.gpt` file in the cloned repo, like this:
+
+```yaml
+tools: google-image from ./search/tool.gpt, sys.download
+
+Search for images of pandas and download one.
+```
+
+:::tip
+You must always specify which tool you are specifically importing from the tool.gpt file, as shown
+in the example above. If no tool is specified, it will default to the first tool defined in the file,
+which currently is `bing`.
+:::
+
+Specific instructions for each search engine follow.
+
+## Bing
+
+The `bing` and `bing-image` tools return search results from the [Bing Web Search API](https://www.microsoft.com/en-us/bing/apis/bing-web-search-api).
+
+The environment variable `GPTSCRIPT_BING_SEARCH_TOKEN` must be set to your API key in order for it to work.
+
+## Brave
+
+The `brave` and `brave-image` tools return search results from the [Brave Search API](https://brave.com/search/api/).
+
+The environment variable `GPTSCRIPT_BRAVE_SEARCH_TOKEN` must be set to your API key in order for it to work.
+
+## DuckDuckGo
+
+The `duckduckgo` tool returns search results from the [DuckDuckGo HTML-only Site](https://html.duckduckgo.com).
+
+No API key is required to use this tool.
+
+By default, this tool will make an HTTP request to DuckDuckGo and parse the results.
+If you do this enough times, it will start to get rate limited.
+Rate limits can be more easily avoided by using Google Chrome in headless mode.
+The tool will do this if the `GPTSCRIPT_USE_CHROME` environment variable is set to `true`.
+
+## Google
+
+The `google` and `google-image` tools return search results from the [Google Custom Search JSON API](https://developers.google.com/custom-search/v1/overview).
+
+The environment variable `GPTSCRIPT_GOOGLE_SEARCH_TOKEN` must be set to your API key in order for it to work,
+and `GPTSCRIPT_GOOGLE_SEARCH_ENGINE_ID` must be set to your Programmable Search Engine's engine ID.