README.md: Update with cmake info.

README.md

@@ -4,17 +4,37 @@ A simple 2D Game engine from scratch!
 
 ## Compiling
 
-This project uses [bam](http://matricks.github.io/bam/) build system
-(Version 0.5 or greater) to compile the engine.
+This project uses [cmake](https://cmake.org) build system
+(Version 3.15 or greater) to compile the engine.
 
-Just running `bam` in this directory will start build the source.
+### Linux with make.
+```
+$ mkdir build
+$ cd build
+$ cmake .. -G "Unix Makefiles"
+$ make
+```
+
+### Windows using NMake
+```
+$ mkdir build
+$ cd build
+$ cmake .. -G "NMake Makefiles"
+$ nmake
+```
+
+### Or the best way (in my opinion)
+install [Ninja](https://ninja-build.org) and run
+```
+$ mkdir build
+$ cd build
+$ cmake .. -G Ninja
+$ ninja
+```
 
 The build will produce `spectre.lib` in the `build` directory that
 should be used when linking.
 
-You will also need to link against `FreeType2` that is located in
-`vendor/FreeType2/lib/x<86|64>/freetype-s.lib` (or `freetype-d-s.lib`
-for debug version)
 
 ## Author