Slightly expand the draft.

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

content/blog/01_spa_agda_lattices.md

@@ -283,6 +283,7 @@ to in the main body of the text). The same is true for the set union and
 intersection operations, \((\cup)\) and \((\cap)\).
 {{< /sidenote >}}". For example, \((+\ \sqcap\ ?)\ =\ +\), because a variable
 that's both "any sign" and "positive" must be positive.
+{#lub-glub-or-and}
 
 There's just one hiccup: what's the greatest lower bound of `+` and `-`?
 it needs to be a value that's less than both of them, but so far, we don't have