docs(plugins/core): add missing documentation about optimize [skip ci]

source/plugins/core/README.md

@@ -203,7 +203,7 @@ It is possible to configure output behaviour using `output_action` option, which
 - `gist`, where output will be stored an already existing gist
   - To use this feature, a `gists` scope must be granted to your `token` and `committer_gist` identifier must be provided
 
-It also possible to alter output condition using `output_action` option, which can be set to:
+It also possible to alter output condition using `output_condition` option, which can be set to:
 - `always`, to always push changes (provided that git sha changed)
 - `data-changed`, to skip changes if no actual data changed (e.g. when only render timestamp changed)
 
@@ -265,6 +265,8 @@ It could then be processed for other usages.
 
 It is possible to convert output to PDF when using a markdown template by setting `config_output` to `markdown-pdf`.
 
+It is advised to keep `config_base64: yes` to encode embed images in base64 and make self-contained documents.
+
 #### ℹ️ Examples workflows
 
 ```yaml
@@ -274,6 +276,31 @@ It is possible to convert output to PDF when using a markdown template by settin
     markdown: template.md
     markdown_cache: .cache
     config_output: markdown-pdf
+    config_base64: yes
+```
+
+### 🗜️ Optimize SVG output
+
+It is possible to optimize SVG output and reducing its filesize to improve loading times and reduce storage.
+
+The following optimizations are supported:
+- `css`, which purge unused CSS and minify remaining styles
+- `xml`, which pretty-print XML (it also helps reducing diffs between commits)
+- `svg`, which optimize SVG with SVGO (experimental)
+
+#### ℹ️ Examples workflows
+
+```yaml
+- uses: lowlighter/metrics@latest
+  with:
+    # ... other options
+    optimize: css, xml
+
+- uses: lowlighter/metrics@latest
+  with:
+    # ... other options
+    optimize: css, xml, svg
+    experimental_features: --optimize-svg
 ```
 
 ### ✨ Render `Metrics insights` statically