update docs (#358)

* update docs

Signed-off-by: wanjunlei <wanjunlei@kubesphere.io>

* Update content/en/docs/concepts/build_strategy.md

---------

Signed-off-by: wanjunlei <wanjunlei@kubesphere.io>
Co-authored-by: Benjamin Huo <huobj@qq.com>

Author: wanjunlei

content/en/docs/concepts/build_strategy.md

@@ -21,6 +21,8 @@ The following are the parameters of the `openfunction` ClusterBuildStrategy:
 | Name | Type | Describe |  
 | --- | --- | --- |
 | RUN_IMAGE | string | Reference to a run image to use |  
+| CACHE_IMAGE | string | Cache Image is a way to preserve cache layers across different builds, which can improve build performance when building functions or applications with lots of dependencies like Java functions. |  
+| BASH_IMAGE | string | The bash image that the strategy used.  |  
 | ENV_VARS  | string | Environment variables to set during _build-time_. The formate is `key1=value1,key2=value2`. |
 
 Users can set these parameters like this:

content/en/docs/concepts/function_trigger.md

@@ -4,7 +4,7 @@ linkTitle: "Function Trigger"
 weight: 3200
 description: 
 ---
-Function `Triggers` are used to define how to trigger a function. Currently, there are two kinds of triggers: `HTTP Trigger`, and `Dapr Trigger`.
+Function `Triggers` are used to define how to trigger a function. Currently, there are two kinds of triggers: `HTTP Trigger`, and `Dapr Trigger`. The default trigger is `HTTP trigger`.
 
 ## HTTP Trigger