Adds reference page on diagnostic tools (ipfs#1532)

Author: ElPaisano

docs/.vuepress/config.js

@@ -251,6 +251,7 @@ module.exports = {
             }
           ],
           '/reference/': [
+            '/reference/diagnostic-tools',
             '/reference/http/gateway',
             '/reference/js/api',
             '/reference/go/api',

docs/reference/diagnostic-tools.md

@@ -0,0 +1,61 @@
+---
+title:  Diagnostic tools
+description: Diagnostic tools to assist with debugging, troubleshooting, and developing with IPFS.
+---
+
+# Diagnostic tools
+
+The IPFS ecosystem contains various open-source tools for the investigation, diagnosis and troubleshooting of common issues that occur when using an IPFS implementation or tool. Tools along with a summary of functionality are listed below.
+
+## IPLD Explorer
+
+[IPLD Explorer](https://explore.ipld.io/) allows you to visualize and explore the IPLD DAG representing a given CID or CAR file. The tool provides the following featured datasets to explore:
+
+- [Project Apollo archives](https://explore.ipld.io/#/explore/QmSnuWmxptJZdLJpKRarxBMS2Ju2oANVrgbr2xWbie9b2D)
+- [IGIS Git repository](https://explore.ipld.io/#/explore/baf4bcfg4ep767tjp5lxyanx5urpjjgx5q2volvy)
+- [An Ethereum block](https://explore.ipld.io/#/explore/bagiacgzah24drzou2jlkixpblbgbg6nxfrasoklzttzoht5hixhxz3rlncyq)
+- [XKCD archives](https://explore.ipld.io/#/explore/QmdmQXB2mzChmMeKY47C43LxUdg1NDJ5MWcKMKxDu7RgQm)
+
+## IPFS check
+
+[IPFS check](https://check.ipfs.network/) determines the retrievability of a given CID from an IPFS node given its multiaddress. Each error type output by the tool can indicate a solution to your problem:
+
+- **Could not connect to the multiaddr** indicates that machines on the internet cannot talk to your machine. Fix your firewall, add port forwarding, or use a relay.
+- **Could not find address in the dht** indicates that your machine is either not connected to the IPFS Public DHT (even as a client), or it is not advertising the address that you are using to test.
+- **Multihash not advertised in the dht** indicates that your machine has not advertised that it has the requested content in the IPFS Public DHT. If you're using kubo, enable the [Accelerated DHT Client](https://github.com/ipfs/go-ipfs/blob/master/docs/experimental-features.md#accelerated-dht-client).
+- **Peer has not responded that it has the CID** indicates that your node cannot find the data that you believe it has, or that there may be some other sort of network latency.
+
+## CID inspector
+
+[CID inspector](http://cid.ipfs.tech/) breaks down a given CID into information that can be useful for understanding CIDs. Specifically, the tool provides:
+
+- A human-readable form of the CID
+- Information on the CID components 
+- The length of the binary and Base32 encoded CID
+- The CIDv1 representation, if applicable
+
+:::callout
+Learn more about CID concepts, including components and versions in the [content addressing concepts guide](../concepts/content-addressing.md).
+:::
+
+## IPFS Gateway Checker
+
+IPFS [Gateway Checker]() provides status information for public IPFS gateways. This information is useful in deciding on which public gateway provider to use, or troubleshooting problems with your current public gateway provider.
+
+## DAG builder visualiser
+
+[DAG builder visualiser](https://dag.ipfs.tech/) allows you to upload a CAR file and visualize it as a DAG. You can toggle parameters that determine how the DAG will be visualized, such as typ (Balanced, Trickle, Flat) and max amount of children.
+
+## CAR Builder
+
+[CAR Builder](https://car.ipfs.io/) allows you to upload a data file and export it as an IPFS CAR file. The tool automatically chunks and hashes your files to automatically produce an IPFS compatible content-addressed archive.
+
+## pl-diagnose
+
+[pl-diagnose](https://pl-diagnose.on.fleek.co/#/diagnose/access-content) is a browser-based software application that automates diagnosis of various issues with an IPFS node. Specifically, this tool can help you answer these questions:
+
+- Is a given CID available on the IPFS network and, if so, which peers are listed in the DHT as providers?
+- Which addresses are listed in the DHT for a given IPFS node?
+- Is an IPFS node accessible by other peers?
+- Is specific content available from an IPFS node?
+