Add documentation about CLI command open-step

Author: ubruhin

modules/cli/nav.adoc

@@ -3,3 +3,4 @@
 ** xref:help.adoc[]
 ** xref:open-library.adoc[]
 ** xref:open-project.adoc[]
+** xref:open-step.adoc[]

modules/cli/pages/open-step.adoc

@@ -0,0 +1,57 @@
+= Command "open-step"
+
+This command opens a STEP file and lets you execute some tasks with it.
+
+.Command
+[source,bash]
+----
+./librepcb-cli open-step --help
+----
+
+.Output
+----
+Usage: ./librepcb-cli [options] open-step [command_options] file
+LibrePCB Command Line Interface
+
+Options:
+  -h, --help        Print this message.
+  -V, --version     Displays version information.
+  -v, --verbose     Verbose output.
+  --minify          Minify the STEP model before validating it. Use in
+                    conjunction with '--save-to' to save the output of the
+                    operation.
+  --tesselate       Tesselate the loaded STEP model to check if LibrePCB is
+                    able to render it. Reports failure (exit code = 1) if no
+                    content is detected.
+  --save-to <file>  Write the (modified) STEP file to this output location (may
+                    be equal to the opened file path). Only makes sense in
+                    conjunction with '--minify'.
+
+Arguments:
+  open-step         Open a STEP model to execute STEP-related tasks outside of
+                    a library.
+  file              Path to the STEP file (*.step).
+----
+
+== Examples
+
+[discrete]
+=== Minify & Validate STEP File
+
+.Command
+[source,bash]
+----
+./librepcb-cli open-step --minify --tesselate --save-to minified.step model.step
+----
+
+.Output
+----
+Open STEP file 'model.step'...
+Perform minify...
+ - Minified from 512,464 bytes to 313,374 bytes (-39%)
+Save to 'out.step'...
+Load model...
+Tesselate model...
+ - Built 17616 vertices with 2 different colors
+SUCCESS
+----