feat: Export frontend functions

Pantograph/Frontend/Basic.lean

@@ -8,6 +8,7 @@ namespace Lean.FileMap
 /-- Extract the range of a `Syntax` expressed as lines and columns. -/
 -- Extracted from the private declaration `Lean.Elab.formatStxRange`,
 -- in `Lean.Elab.InfoTree.Main`.
+@[export pantograph_frontend_stx_range]
 protected def stxRange (fileMap : FileMap) (stx : Syntax) : Position × Position :=
   let pos    := stx.getPos?.getD 0
   let endPos := stx.getTailPos?.getD pos

Pantograph/Frontend/Elab.lean

@@ -88,6 +88,7 @@ structure TacticInvocation where
 namespace TacticInvocation
 
 /-- Return the range of the tactic, as a pair of file positions. -/
+@[export pantograph_frontend_tactic_invocation_range]
 protected def range (t : TacticInvocation) : Position × Position := t.ctx.fileMap.stxRange t.info.stx
 
 /-- Pretty print a tactic. -/