Rollup merge of #49742 - Pulkit07:master, r=steveklabnik

Using X headings instead of 0.X #49739

Fix #49739

src/doc/index.md

@@ -13,65 +13,65 @@ unofficial documentation resources as well!
 Many of these resources take the form of "books"; we collectively call these
 "The Rust Bookshelf." Some are large, some are small.
 
-## Learn Rust
+# Learn Rust
 
 If you'd like to learn Rust, this is the spot for you! All of these resources
 assume that you have programmed before, but not in any specific language:
 
-### The Rust Programming Language
+## The Rust Programming Language
 
 Affectionately nicknamed "the book," [The Rust Programming
 Language](book/index.html) will give you an overview of the language from
 first principles. You'll build a few projects along the way, and by the end,
 you'll have a solid grasp of the language.
 
-### Rust By Example
+## Rust By Example
 
 If reading multiple hundreds of pages about a language isn't your style, then
 [Rust By Example](rust-by-example/index.html) has you covered. While the book talks about code with
 a lot of words, RBE shows off a bunch of code, and keeps the talking to a
 minimum. It also includes exercises!
 
-## Use Rust
+# Use Rust
 
 Once you've gotten familliar with the language, these resources can help you
 when you're actually using it day-to-day.
 
-### The Standard Library
+## The Standard Library
 
 Rust's standard library has [extensive API documentation](std/index.html),
 with explanations of how to use various things, as well as example code for
 accomplishing various tasks.
 
-### The Cargo Book
+## The Cargo Book
 
 [The Cargo Book](cargo/index.html) is a guide to Cargo, Rust's build tool and dependency manager.
 
-### The Rustdoc Book
+## The Rustdoc Book
 
 [The Rustdoc Book](rustdoc/index.html) describes our documentation tool, `rustdoc`.
 
-### Extended Error Listing
+## Extended Error Listing
 
 Many of Rust's errors come with error codes, and you can request extended
 diagnostics from the compiler on those errors. You can also [read them
 here](error-index.html), if you prefer to read them that way.
 
-## Master Rust
+# Master Rust
 
 Once you're quite familiar with the language, you may find these advanced
 resources useful.
 
-### The Reference
+## The Reference
 
 [The Reference](reference/index.html) is not a formal spec, but is more detailed and
 comprehensive than the book.
 
-### The Rustonomicon
+## The Rustonomicon
 
 [The Rustonomicon](nomicon/index.html) is your guidebook to the dark arts of unsafe
 Rust. It's also sometimes called "the 'nomicon."
 
-### The Unstable Book
+## The Unstable Book
 
 [The Unstable Book](unstable-book/index.html) has documentation for unstable features.