chore: add docs and example

DOCS.md

@@ -0,0 +1,40 @@
+# Docs
+
+This file is meant to explain how it's working. I'll try to keep it up to date.
+
+## General idea
+
+Meta programming is really useful, in a lots of ways, that's why I'm trying to implement this in C, in the most pleasant way.  
+Header-only libraries are also a must imo, so let's try to implement meta programming within a single header! The same header for both compilation and runtime btw.
+
+## Compilation time
+
+`cmeta.h` contains the code to parse structs, lexing is handled by `stb_c_lexer` (for now).  
+The `bool process_file(const char *file_path)` function calls `gcc -E <file_path>` (so we handle macros etc), then parses the result. It then generates all `Struct_Info`s in a special place in the header, delimited by two `// AUTO GENERATED CODE  //`.  
+If anything has failed, nothing will be generated between the two comments, so cmeta remains intact.  
+
+This struct:
+```c
+typedef struct {
+    int int_field;
+} Foo_Struct;
+```
+
+Will be converted to this:
+```c
+// cmeta.h
+
+// AUTO GENERATED CODE  //
+static Struct_Info foo_struct_info = {
+    .name = "Foo_Struct",
+    .fields_count = 1,
+    .fields = (Field_Info[1]) {
+        { .type = "int", .name = "int_field" },
+    },
+};
+// AUTO GENERATED CODE  //
+```
+
+## Runtime
+
+`cmeta.h` now contains both type infos and useful functions to interact with them.