🩹 Fix HereDoc syntax highlighting bleeding into subsequent recipes

[nefrob]

Description:

Re #73.

• Fix shell HereDoc syntax highlighting bleeding into subsequent recipes by replacing end with while in embedded language rules.

Thanks @RedCMD.

Testing/Screenshots:

[nefrob]

We need the indentation version of the solution proposed in the issue.

From the just docs:

Recipe lines can be indented with spaces or tabs, but not a mix of both. All of a recipe's lines must have the same type of indentation, but different recipes in the same justfile may use different indentation.

Each recipe must be indented at least one level from the recipe-name but after that may be further indented.