Organize API docs

docs/src/api.md

@@ -7,6 +7,54 @@ end
 
 # API Reference
 
-```@autodocs
-Modules = [SequenceVariation]
+## Edits
+
+```@docs
+Substitution
+Deletion
+Insertion
+```
+
+## Variants
+
+```@docs
+Variant
+reference(::Variant)
+variations
+reconstruct!
+```
+
+## Variations
+
+```@docs
+Variation
+reference(::Variation)
+mutation
+translate
+refbases
+altbases
+```
+
+## Private API
+
+### Edits
+
+```@docs
+Edit
+_mutation
+_lendiff
+```
+
+### Variants
+
+```@docs
+_edits
+_is_valid(::Variant)
+```
+
+### Variations
+
+```@docs
+_edit
+_is_valid(::Variation)
 ```