docs: remove cost, document missing options and improve docs (#653)

source/plugins/code/README.md

@@ -24,4 +24,5 @@ Display a random code snippet from your recent activity history.
     plugin_code_load: 100               # Fetch 100 events from activity
     plugin_code_visibility: public      # Only display snippets from public activity
     plugin_code_skipped: github/octocat # Skip github/octocat repository
+    plugin_code_languages: javascript   # Limit code snippets to JavaScript code
 ```

source/plugins/code/metadata.yml

@@ -1,5 +1,4 @@
 name: "♐ Code snippet of the day"
-cost: 1 REST request per 100 events fetched
 category: github
 index: 22
 supports:
@@ -44,7 +43,7 @@ inputs:
     type: array
     format: comma-separated
     default: ""
-    example: my-repo-1, my-repo-2, owner/repo-3 ...
+    example: my-repo-1, my-repo-2, owner/repo-3, ...
 
   # Restrict code snippet languages
   # These are guessed through linguist
@@ -53,4 +52,4 @@ inputs:
     type: array
     format: comma-separated
     default: ""
-    example: javascript, typescript, ....
+    example: javascript, typescript, ...