Replace deprecated learn theme by relearn

relearn is fork of learn

Author: ymd-h

.gitmodules

@@ -1,3 +1,3 @@
-[submodule "themes/learn"]
-	path = site/themes/learn
-	url = https://github.com/matcornic/hugo-theme-learn.git
+[submodule "hugo-theme-relearn"]
+	path = site/themes/hugo-theme-relearn
+	url = https://github.com/McShelby/hugo-theme-relearn.git

site/static/css/custom.css renamed to site/assets/css/custom.css

@@ -3,7 +3,7 @@ languageCode = "en-US"
 defaultContentLanguage = "en"
 
 title = "cpprb"
-theme = "learn"
+theme = "hugo-theme-relearn"
 themesdir = "themes"
 metaDataFormat = "yaml"
 defaultContentLanguageInSubdir= false
@@ -21,7 +21,7 @@ publishDir = "../public"
   custom_css = ["css/custom.css"]
 
 [outputs]
-home = [ "HTML", "RSS", "JSON"]
+home = ['html', 'rss', 'print']
 
 [[menu.shortcuts]]
 name = "<i class='fab fa-fw fa-gitlab'></i> GitLab"