Update documentation

docs/stdlib/string.md

@@ -4,6 +4,10 @@
 
 The `string` module automatically imports the `err` module.  
 
+All the functions are designed to work for the strings in the default encoding.
+If passed a string in an encoding that has a different null terminator,
+then the results are undefined and the program will most likely crash or freeze.
+
 #### `byte strzlen(pointer str)`
 
 Calculates the length of a null-terminated string.  

mkdocs.yml

@@ -23,6 +23,7 @@ nav:
     - Syntax: lang/syntax.md
     - Types: lang/types.md
     - Literals: lang/literals.md
+    - Predefined constants: lang/predefined_constants.md
     - Text encodings: lang/text.md
     - Operators: lang/operators.md
     - Functions: lang/functions.md
@@ -35,6 +36,7 @@ nav:
     - stdio module: stdlib/stdio.md
     - keyboard, err, random: stdlib/other.md
     - joy, mouse, x_coord: stdlib/input.md
+    - encconv module: stdlib/encconv.md
     - Platform-dependent modules: stdlib/frequent.md
     - cbm_file module: stdlib/cbm_file.md
     - C64-only modules: stdlib/c64.md