Adds ByteByteGo guides and links (#106)

This PR adds all the guides from [Visual
Guides](https://bytebytego.com/guides/) section on bytebytego to the
repository with proper links.

- [x] Markdown files for guides and categories are placed inside
`data/guides` and `data/categories`
- [x] Guide links in readme are auto-generated using
`scripts/readme.ts`. Everytime you run the script `npm run
update-readme`, it reads the categories and guides from the above
mentioned folders, generate production links for guides and categories
and populate the table of content in the readme. This ensures that any
future guides and categories will automatically get added to the readme.
- [x] Sorting inside the readme matches the actual category and guides
sorting on production

data/guides/design-gmail.md

@@ -0,0 +1,26 @@
+---
+title: "Design Gmail"
+description: "Explore the design of Gmail: from sending to receiving emails."
+image: "https://assets.bytebytego.com/diagrams/0184-email.jpg"
+createdAt: "2024-03-01"
+draft: false
+categories:
+  - how-it-works
+tags:
+  - "Email"
+  - "System Design"
+---
+
+![](https://assets.bytebytego.com/diagrams/0184-email.jpg)
+
+One picture is worth more than a thousand words. In this post, we will take a look at what happens when Alice sends an email to Bob.
+
+## Sending an Email: A Step-by-Step Guide
+
+1.  Alice logs in to her Outlook client, composes an email, and presses “send”. The email is sent to the Outlook mail server. The communication protocol between the Outlook client and mail server is SMTP.
+
+2.  Outlook mail server queries the DNS (not shown in the diagram) to find the address of the recipient’s SMTP server. In this case, it is Gmail’s SMTP server. Next, it transfers the email to the Gmail mail server. The communication protocol between the mail servers is SMTP.
+
+3.  The Gmail server stores the email and makes it available to Bob, the recipient.
+
+4.  Gmail client fetches new emails through the IMAP/POP server when Bob logs in to Gmail.