Add KCL constants for sweep relativeTo strings (#6974)

* Add KCL constants for sweep relativeTo strings

Before:

```
sweep(pill, path = sweepPath, relativeTo = "trajectoryCurve")
```

After:

```
sweep(pill, path = sweepPath, relativeTo = sweep::TRAJECTORY)
```

* Update docs

docs/kcl-std/consts/std-sweep-SKETCH_PLANE.md

@@ -0,0 +1,16 @@
+---
+title: "sweep::SKETCH_PLANE"
+subtitle: "Constant in std::sweep"
+excerpt: "Local/relative to a position centered within the plane being sketched on"
+layout: manual
+---
+
+Local/relative to a position centered within the plane being sketched on
+
+```kcl
+sweep::SKETCH_PLANE: string = 'sketchPlane'
+```
+
+
+
+

docs/kcl-std/consts/std-sweep-TRAJECTORY.md

@@ -0,0 +1,16 @@
+---
+title: "sweep::TRAJECTORY"
+subtitle: "Constant in std::sweep"
+excerpt: "Local/relative to the trajectory curve"
+layout: manual
+---
+
+Local/relative to the trajectory curve
+
+```kcl
+sweep::TRAJECTORY: string = 'trajectoryCurve'
+```
+
+
+
+