docs: add resolver chapter

Signed-off-by: Nico Braun <[email protected]>

docs/src/SUMMARY.md

@@ -14,6 +14,7 @@
     - [Pull Requests](./configuration/pull-requests.md)
     - [Scopes](./configuration/scopes.md)
     - [File Associations](./configuration/file-associations.md)
+  - [Resolvers](./configuration/resolvers.md)
   - [Registry Auth](./configuration/registry-auth.md)
 - [Deployment](./deployment/index.md)
   - [Kubernetes](./deployment/kubernetes.md)

docs/src/configuration/file-associations.md

@@ -1,8 +1,5 @@
 # File Associations
 
-In order to find image references, the file must be of a known type. Currently
-known types are `kubernetes`, `docker-compose` and `ko-build`.
-
 The type of a given yaml file is determined by using glob to math the filename.
 The default matching rules look like this:
 
@@ -28,5 +25,4 @@ subscriptions:
         pattern: "*"
 ```
 
-> **Note** If there is a filetype you would to use, that is currently not
-supported, please open and issue so we can  can add it to the codebase.
+If the builtin resolvers are not sufficient. You can [create your own resolver](./resolvers.md).

docs/src/configuration/resolvers.md

@@ -0,0 +1,17 @@
+# Resolvers
+
+It is possible to create custom resolvers, to look up image references in yaml
+files.
+
+```yaml
+resolvers:
+  - name: my-custom
+    paths:
+      - path.to.image
+      - another.path
+```
+
+If a resolvers is used, via a [file association](./file-associations.md), image
+references at all paths of the resolver are handled. Kobold does not stop on
+first match. Additionally, if a path does not exist, kobold will continue with
+the next path, without error or warning.