Sketcher docs: add 1.2 feature notes (Text, Group, Projection, Polyline, Merge)

[mkcash]

Summary

• Updates 5 Sketcher Workbench wiki pages with FreeCAD 1.2 features:

1. Sketcher_CreateText – Corrected version tag from 1.1 to 1.2; the Text tool was added in v1.2 (FreeCAD/FreeCAD#22217).

2. Sketcher_ConstrainGroup – Corrected version tag from 1.1 to 1.2; the Group constraint was added in v1.2 (#22217).

3. Sketcher_Projection – Bézier curves and Offset curves can now be imported as external geometry (#25144).

4. Sketcher_CreatePolyline – The polyline tool has been reworked with On-View-Parameter (OVP) support for inline numeric input (#29336).

5. Sketcher_MergeSketches – Merge now imports external geometry, remaps constraints referencing external geometry, and creates the merged sketch in the shared Body (#29497).

Validation

• git diff --check HEAD^ HEAD

Addresses #94.

[Reqrefusion]

Do not add T tags yourself; only modify the files in the wiki root directory, do not touch the translation files. Please check the latest version and ensure that the information you are adding has not been added previously. Also, be sure to cite the source of your change. Regression corrections should not be added to the documentation. And it should never contain information that the end user shouldn't know.