Add non-Ubuntu Linux build instructions to the README (#102)

Largely based on @umireon's [AUR build script](#62 (comment)), these steps worked for me on a
Gentoo Linux system as well, so I figured it might be helpful to add them to
the README.

I feel like some of this could be merged with the Ubuntu section above (which
might also in itself be applicable to Debian as well as Ubuntu), but for now
this should at least help people

README.md

@@ -96,9 +96,11 @@ $ ./.github/scripts/package-macos -c Release
 ```
 (Note that maybe the outputs will be in the `Release` folder and not the `install` folder like `pakage-macos` expects, so you will need to rename the folder from `build_x86_64/Release` to `build_x86_64/install`)
 
-### Linux (Ubuntu)
+### Linux
+
+#### Ubuntu
 
-For successfully building on linux, first clone the repo, then from the repo directory:
+For successfully building on Ubuntu, first clone the repo, then from the repo directory:
 ```sh
 $ sudo apt install -y libssl-dev
 $ ./.github/scripts/build-linux
@@ -119,6 +121,42 @@ $ mkdir -p ~/.config/obs-studio/plugins/obs-localvocal/data
 $ cp -R release/RelWithDebInfo/share/obs/obs-plugins/obs-localvocal/* ~/.config/obs-studio/plugins/obs-localvocal/data/
 ```
 
+#### Other distros
+
+For other distros where you can't use the CI build script, you can build the plugin as follows
+
+1. Clone the repository and install these dependencies using your distribution's package manager:
+
+    * libssl (with development headers)
+
+2. Generate the CMake build scripts (adjust folders if necessary)
+
+    ```sh
+    cmake -B build-dir --preset linux-x86_64 -DUSE_SYSTEM_CURL=ON -DCMAKE_INSTALL_PREFIX=./output_dir
+    ```
+
+3. Build the plugin and copy the files to the output directory
+
+    ```sh
+    cmake --build build-dir --target install
+    ```
+
+4. Copy plugin to OBS plugins folder
+
+    ```sh
+    mkdir -p ~/.config/obs-studio/plugins/bin/64bit
+    cp -R ./output_dir/lib/obs-plugins/* ~/.config/obs-studio/plugins/bin/64bit/
+    ```
+
+    > N.B. Depending on your system, the plugin might be in `./output_dir/lib64/obs-plugins` instead.
+
+5. Copy plugin data to OBS plugins folder - Possibly only needed on first install
+
+    ```sh
+    mkdir -p ~/.config/obs-studio/plugins/data
+    cp -R ./output_dir/share/obs/obs-plugins/obs-localvocal/* ~/.config/obs-studio/plugins/data/
+    ```
+
 ### Windows
 
 Use the CI scripts again, for example: