docs(tvix/eval): add "intern literals" to future optimisations

Signed-off-by: Adam Joseph <adam@westernsemico.com>
Change-Id: I460230863de853ca5248733bc977d4780b216f36
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7096
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>

tvix/eval/docs/known-optimisation-potential.md

@@ -104,3 +104,9 @@ optimisations, but note the most important ones here.
 
   This can be avoided, as we statically analyse the scope and should
   be able to tell whether any such logic was required.
+
+* Intern literals [easy]
+
+  Currently, the compiler emits a separate entry in the constant
+  table for each literal.  So the program `1 + 1 + 1` will have
+  three entries in its `Chunk::constants` instead of only one.