Add linux building instructions (#149)

- Do we need to mention that vcpkg should be installed in the first
place?
- Do we need to specify what the difference between release and debug
builds is?
- Are there any other prerequisites for building on windows?

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README.md

@@ -4,7 +4,9 @@ The launcher is the way we communitcate to outside the game, it does a few autom
 
 **To clone this repository**: `git clone --recurse-submodules https://github.com/BeamMP/BeamMP-Launcher.git`
 
-## How to build - Release
+## How to build for Windows
+
+### Release
 
 In the root directory of the project,
 1. `cmake -DCMAKE_BUILD_TYPE=Release . -B bin -DCMAKE_TOOLCHAIN_FILE=C:/vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows-static`
@@ -12,10 +14,41 @@ In the root directory of the project,
 
 Remember to change `C:/vcpkg` to wherever you have vcpkg installed.
 
-## How to build - Debug
+### Debug
 
 In the root directory of the project,
 1. `cmake . -B bin -DCMAKE_TOOLCHAIN_FILE=C:/vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-windows-static`
 2. `cmake --build bin --parallel`
 
 Remember to change `C:/vcpkg` to wherever you have vcpkg installed.
+
+## How to build for Linux
+
+Make sure you have the necessary development tools installed
+
+- Debian: `sudo apt install build-essential`
+- Fedora: `sudo dnf groupinstall "Development Tools"`
+- Arch: `sudo pacman -S base-devel`
+- openSUSE: `zypper in -t pattern devel-basis`
+
+### Release
+
+In the root directory of the project,
+1. `cmake -DCMAKE_BUILD_TYPE=Release . -B bin -DCMAKE_TOOLCHAIN_FILE=/~/vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux`
+2. `cmake --build bin --parallel --config Release`
+
+Remember to change `/~/vcpkg` to wherever you have vcpkg installed.
+
+### Debug
+
+In the root directory of the project,
+1. `cmake . -B bin -DCMAKE_TOOLCHAIN_FILE=/~/vcpkg/scripts/buildsystems/vcpkg.cmake -DVCPKG_TARGET_TRIPLET=x64-linux`
+2. `cmake --build bin --parallel`
+
+Remember to change `/~/vcpkg` to wherever you have vcpkg installed.
+
+## Running out of RAM while building
+
+Should you run out of RAM while building, you can ommit the `--parallel` intruction, it will then use less RAM due to building only on one CPU thread.
+
+You can also specify a number of threads to use, for example `--parallel 4` will use four CPU threads, but due to the small project size, you may be faster just omitting `--parallel` instead of trying to find the highest possible multithread number