CompatHelper: add new compat entry for Plots at version 1 for package docs, (keep existing compat) (#634)

Co-authored-by: CompatHelper Julia <[email protected]>

Author: github-actions[bot]

docs/Project.toml

@@ -10,5 +10,6 @@ TrixiBase = "9a0f1c46-06d5-4909-a5a3-ce25d3fa3284"
 Documenter = "1"
 DocumenterCitations = "1"
 OrdinaryDiffEq = "6"
+Plots = "1"
 PointNeighbors = "0.4"
 TrixiBase = "0.1"