docs: add new alignment option to docs

docs/source/opt.rst

@@ -0,0 +1,36 @@
+.. default-domain:: C
+
+Options
+===============================================================================
+
+A few options are provided via macros.
+
+Alignment
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+As default, cglm requires types to be aligned. Alignment requirements:
+
+vec3:   8 byte
+vec4:   16 byte
+mat4:   16 byte
+versor: 16 byte
+
+By starting **v0.4.5** cglm provides an option to disable alignment requirement.
+To enable this option define **CGLM_ALL_UNALIGNED** macro before all headers.
+You can define it in Xcode, Visual Studio (or other IDEs) or you can also prefer
+to define it in build system. If you use pre-compiled verisons then you
+have to compile cglm with **CGLM_ALL_UNALIGNED** macro.
+
+**VERY VERY IMPORTANT:** If you use cglm in multiple projects and
+ those projects are depends on each other, then
+
+ | *ALWAYS* or *NEVER USE* **CGLM_ALL_UNALIGNED** macro in linked projects
+
+ if you do not know what you are doing. Because a cglm header included
+ via 'project A' may force types to be aligned and another cglm header
+ included via 'project B' may not require alignment. In this case
+ cglm functions will read from and write to **INVALID MEMORY LOCATIONs**.
+
+ ALWAYS USE SAME CONFIGURATION / OPTION for **cglm** if you have multiple projects.
+
+ For instance if you set CGLM_ALL_UNALIGNED in a project then set it in other projects too