chore: rebrand Nix to Lix when it makes sense

Here's my guide so far:

$ rg '((?!(recursive).*) Nix
(?!(daemon|store|expression|Rocks!|Packages|language|derivation|archive|account|user|sandbox|flake).*))'
-g '!doc/' --pcre2

All items from this query have been tackled. For the documentation side:
that's for https://git.lix.systems/lix-project/lix/issues/162.

Additionally, all remaining references to github.com/NixOS/nix which
were not relevant were also replaced.

Fixes: https://git.lix.systems/lix-project/lix/issues/148.
Fixes: https://git.lix.systems/lix-project/lix/issues/162.
Change-Id: Ib3451fae5cb8ab8cd9ac9e4e4551284ee6794545
Signed-off-by: Raito Bezarius <raito@lix.systems>

doc/manual/src/contributing/hacking.md

@@ -137,7 +137,7 @@ You can also build Lix for one of the [supported platforms](#platforms).
 
 Lix can be built for various platforms, as specified in [`flake.nix`]:
 
-[`flake.nix`]: https://github.com/nixos/nix/blob/master/flake.nix
+[`flake.nix`]: https://git.lix.systems/lix-project/lix/src/branch/main/flake.nix
 
 - `x86_64-linux`
 - `x86_64-darwin`

doc/manual/src/installation/obtaining-source.md

@@ -1,13 +1,13 @@
 # Obtaining the Source
 
-The most recent sources of Nix can be obtained from its [Git
-repository](https://github.com/NixOS/nix). For example, the following
+The most recent sources of Lix can be obtained from its [Git
+repository](https://git.lix.systems/lix-project/lix). For example, the following
 command will check out the latest revision into a directory called
 `nix`:
 
 ```console
-$ git clone https://github.com/NixOS/nix
+$ git clone https://git.lix.systems/lix-project/lix
 ```
 
 Likewise, specific releases can be obtained from the
-[tags](https://github.com/NixOS/nix/tags) of the repository.
+[tags](https://git.lix.systems/lix-project/lix/tags) of the repository.

doc/manual/src/quick-start.md

@@ -22,7 +22,7 @@ to subsequent chapters.
    $ curl -sSf -L https://install.lix.systems/lix | sh -s -- install
    ```
 
-   For systems that **already have Nix installed**, such as NixOS systems, read our [install page](https://lix.systems/install)
+   For systems that **already have a Nix implementation installed**, such as NixOS systems, read our [install page](https://lix.systems/install)
 
    The install script will use `sudo`, so make sure you have sufficient rights.