update to latest PreTeXt project found in `/home/runner/work/pretext-…

…cli/pretext-cli`.

�[31merror: �[0mA project already exists in `/home/runner/work/pretext-cli/pretext-cli` (it contains the file `project.ptx`).
�[31merror: �[0mNo new project will be generated.

----------------------------------------------------
While running pretext, the following errors occurred:

(see log messages above or in the 'logs' folder for more information)
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project.ptx

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
-<!-- This file was automatically generated by PreTeXt 2.12.0. -->
+<!-- This file was automatically generated by PreTeXt 2.13.1. -->
 <!-- If you modify this file, PreTeXt will no longer automatically update it.-->
 
 <!-- This file, the project manifest, provides the overall configuration for your PreTeXt project. To edit the content of your document, open `source/main.ptx`. See https://pretextbook.org/doc/guide/html/processing-CLI.html#cli-project-manifest. -->
@@ -22,6 +22,7 @@
         stage="output/stage"
         xsl="xsl"
         asy-method="server"
+        generated-cache=".cache"
      >
        <targets>
           <target

publication/publication.ptx

@@ -142,19 +142,11 @@
         exercise-readingquestion="no"
       />-->
 
-    <!-- Specify the style of the html by giving names to      -->
-    <!-- override defaults.  Ex: to use "style_oscarlevin.css" -->
-    <!-- put <css style="oscarlevin"/>                         -->
+    <!-- Specify the theme for the html by giving names to     -->
+    <!-- override defaults.  Ex:<css theme="denver"/>          -->
     <!-- See also                                              -->
     <!-- https://pretextbook.org/doc/guide/html/publication-file-online.html#online-style-options -->
-      <!--<css
-          style="oscarlevin"
-          colors="blue_red"
-          knowls="crc"
-          toc="crc"
-          banner="crc"
-          navbar="crc"
-      />-->
+      <!--<css theme="denver"/>-->
 
     <!-- Search can be default or none, or you can use a Google-cx number to use google's search
     feature (but then variant should be set to none to avoid conflict) -->

requirements.txt

@@ -1,2 +1,2 @@
-# This file was automatically generated with PreTeXt 2.12.0.
-pretext == 2.12.0
+# This file was automatically generated with PreTeXt 2.13.1.
+pretext == 2.13.1