docs: add pointer to pre-built binary releases
Users now have the option of installing from source or directly
installing a binary.
I also corrected some text that effectively said that installing a Nix
flake is not installing from source, but I think it actually does
install from source.
@@ -129,11 +129,15 @@ scripts if requested.
## Installation
+See below for how to build from source. There are also
+[pre-built binaries](https://github.com/martinvonz/jj/releases) for Windows,
+Mac, or Linux (musl).
+
### Linux
-On most distributions, you'll need to install from source.
+On most distributions, you'll need to build from source using `cargo` directly.
-#### From source
+#### Build using `cargo`
First make sure that you have the `libssl-dev` and `openssl` packages installed
by running something like this:
