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>

ib002/10-graphs/2021-05-18-iterative-and-iterators.md

@@ -1,4 +1,5 @@
 ---
+id: iterative-and-iterators
 title: Iterative algorithms via iterators
 description: |
   Iterative DFS using iterators.
@@ -7,6 +8,8 @@ tags:
 - graphs
 - iterators
 - iterative
+last_update:
+  date: 2021-05-18
 ---
 
 ## Introduction

ib002/10-graphs/2022-04-30-bfs-tree.mdx

@@ -1,10 +1,13 @@
 ---
+id: bfs-tree
 title: Distance boundaries from BFS tree on undirected graphs
 description: |
   Short explanation of distance boundaries deduced from a BFS tree.
 tags:
 - graphs
 - bfs
+last_update:
+  date: 2022-04-30
 ---
 
 import ThemedSVG from "@site/src/components/ThemedSVG";