Updated documentation

src/readme.md

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+## Documentation
+
+### [main.go](/main.go)
+
+Entry point. It simply calls `cli.Main` which we can use for testing.
+
+### [src/cli/Main.go](/src/cli/Main.go)
+
+The command line interface expects a command like `build` as the first argument.
+Commands are implemented as functions in the [src/cli](src/cli) directory.
+Each command has its own set of parameters.
+
+### [src/cli/Build.go](/src/cli/Build.go)
+
+The build command creates a new `Build` instance with the given directory and calls the `Run` method.
+
+If no directory is specified, it will use the current directory.
+
+If the `--dry` flag is specified, it will perform all tasks except the final write to disk.
+This flag should be used in most tests and benchmarks to avoid needless disk writes.
+
+```shell
+q build
+q build examples/hello
+q build examples/hello --dry
+```
+
+Adding the `-a` or `--assembler` flag shows the generated assembly instructions:
+
+```shell
+q build examples/hello -a
+```
+
+Adding the `-v` or `--verbose` flag shows verbose compiler information:
+
+```shell
+q build examples/hello -v
+```
+
+### [src/build/Build.go](/src/build/Build.go)
+
+The `Build` type defines all the information needed to start building an executable file.
+The name of the executable will be equal to the name of the build directory.
+
+`Run` starts the build which will scan all `.q` source files in the build directory.
+Every source file is scanned in its own goroutine for performance reasons.
+Parallelization here is possible because the order of files in a directory is not significant.
+
+The main thread is meanwhile waiting for new function objects to arrive from the scanners.
+Once a function has arrived, it will be stored for compilation later.
+We need to wait with the compilation step until we have enough information about all identifiers from the scan.
+
+Then all the functions that were scanned will be compiled in parallel.
+We create a separate goroutine for each function compilation.
+Each function will then be translated to generic assembler instructions.
+
+All the functions that are required to run the program will be added to the final assembler.
+The final assembler resolves label addresses, optimizes the performance and generates the specific x86-64 machine code from the generic instruction set.
+
+### [src/core/Function.go](/src/core/Function.go)
+
+This is the "heart" of the compiler.
+Each function runs `f.Compile` which organizes the source code into an abstract syntax tree that is then compiled via `f.CompileAST`.
+You can think of AST nodes as the individual statements in your source code.
+
+### [src/ast/Parse.go](/src/ast/Parse.go)
+
+This is what generates the AST from tokens.
+
+### [src/expression/Parse.go](/src/expression/Parse.go)
+
+This is what generates expressions from tokens.