Merge pull request #105 from sunfishcode/sunfishcode/docs

Add subsection headers for the mangling documentation.

Author: lukewagner

design/mvp/CanonicalABI.md

@@ -1429,7 +1429,9 @@ character in a component-level import/export (as is currently the case in `wit`
 [identifiers](WIT.md#identifiers)) and thus can safely be used to prefix
 auxiliary Canonical ABI-induced imports/exports.
 
-Instance-mangling recursively builds a dotted path string (of instance names)
+#### Instance type mangling
+
+Instance-type mangling recursively builds a dotted path string (of instance names)
 that is included in the mangled core import/export name:
 ```python
 def mangle_instances(xs, path = ''):
@@ -1457,7 +1459,9 @@ def mangle_instances(xs, path = ''):
 The three `TODO` cases are intended to be filled in by future PRs extending
 the Canonical ABI.
 
-Function and value types are recursively mangled into
+#### Function type mangling
+
+Function types are mangled into
 [`wit`](WIT.md)-compatible syntax:
 ```python
 def mangle_funcname(name, ft):
@@ -1473,6 +1477,11 @@ def mangle_funcvec(es, pre_space):
   mangled_elems = (e[0] + ': ' + mangle_valtype(e[1]) for e in es)
   return '(' + ', '.join(mangled_elems) + ')'
 
+#### Value type mangling
+
+Value types are similarly mangled into [`wit`](WIT.md)-compatible syntax,
+recursively:
+
 def mangle_valtype(t):
   match t:
     case Bool()           : return 'bool'