cron: add alias page (#9388)

* cron: add alias page

* cron: remove trailing whitespace

* ripgrep: use standard alias description

* todoman: use standard alias description

pages/common/cron.md

@@ -0,0 +1,8 @@
+# cron
+
+> `cron` is a system scheduler for running jobs or tasks unattended.
+> The command to submit, edit or delete entries to `cron` is called `crontab`.
+
+- View documentation for the original command:
+
+`tldr crontab`

pages/common/ripgrep.md

@@ -2,6 +2,6 @@
 
 > `ripgrep` is the common name for the command `rg`.
 
-- View documentation for the actual command:
+- View documentation for the original command:
 
 `tldr rg`

pages/common/todoman.md

@@ -4,6 +4,6 @@
 > `todoman` is a common name for the command `todo`, but not a command itself.
 > More information: <https://todoman.readthedocs.io/>.
 
-- View documentation for the actual command:
+- View documentation for the original command:
 
 `tldr todo`