Fix slugs and add example of constant propagation

Signed-off-by: Danila Fedorin <danila.fedorin@gmail.com>

content/blog/08_spa_agda_forward/index.md

@@ -415,6 +415,10 @@ plus [ z₁ ]ᶜ [ z₂ ]ᶜ = [ z₁ Int.+ z₂ ]ᶜ
 
 we can defined a constant-propagation analysis.
 
+```
+{"neg" ↦ -1, "pos" ↦ 1, "unknown" ↦ 0, "zero" ↦ 0, }
+```
+
 However, we haven't proved our analysis correct, and we haven't yet made use of
 the CFG-semantics equivalence that we
 [proved in the previous section]({{< relref "07_spa_agda_semantics_and_cfg" >}}).