docs: add docs for clanLib

docs/.gitignore

@@ -1,4 +1,5 @@
 /site/reference
+!/site/reference/clanLib/index.md
 /site/services/official
 /site/static
 /site/option-search

docs/mkdocs.yml

@@ -140,6 +140,7 @@ nav:
           - reference/cli/vars.md
           - reference/cli/vms.md
 
+      - clanLib: reference/clanLib/index.md
       - HTTP API: api.md
 
       - Decisions:

docs/site/reference/clanLib/index.md

@@ -0,0 +1,18 @@
+`clanLib` is a collection of functions and utilities
+
+!!! Danger
+    unless explicitly mentioned everything in ClanLib is for internal use in clan-core.
+
+## Stable Attributes
+
+The following attributes are publicly maintained
+
+### `clanLib.clan`
+
+A function that takes [clan options](../../reference/options/clan.md)
+The option definitions can be composed by means of `imports`
+
+Returns an evaluated clan configuration - A `lib.evalModules` result:
+
+- `.config`: *The main result*
+- `.options`,`.moduleGraph`, ...: For debugging.