Add vim plugin for syntax highlighting and fix wrong type (WaypointTrajectoryGoal)

fix WaypointTrajectoryGoal and add vim plugin for goal-dsl

Code review checklist

[x] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
[x] Title summarizes what is changing
[x] Commit messages are meaningful (see this for details)
[x] Tests have been included and/or updated
[x] Docstrings have been included and/or updated, as appropriate
[x] Standalone docs have been updated accordingly
[x] Changelog(s) has/have been updated, as needed (see CHANGELOG.md, no need to update for typo fixes and such).