chore: add ‹last_update› to docs-like posts

Allow showing ‹last updated› on the pages and also rename the files
where necessary, so they are shown in the order they were created.

Signed-off-by: Matej Focko <mfocko@redhat.com>

ib002/08-rb-trees/2022-04-05-applications.md

@@ -1,4 +1,5 @@
 ---
+id: applications
 title: Použití červeno-černých stromů
 description: |
   Ukázka použití červeno-černých stromů v standardních knižnicích známých jazyků.
@@ -6,6 +7,8 @@ tags:
 - balanced trees
 - red-black trees
 - applications
+last_update:
+  date: 2022-04-05
 ---
 
 ## Použití

ib002/08-rb-trees/2023-06-10-rules.mdx

@@ -1,10 +1,13 @@
 ---
+id: rules
 title: On the rules of the red-black tree
 description: |
   Shower thoughts on the rules of the red-black tree.
 tags:
 - red-black trees
 - balanced trees
+last_update:
+  date: 2023-06-10
 ---
 
 import ThemedSVG from "@site/src/components/ThemedSVG";