WIP: DOC: Add Technical Reference page for justification codes

doc/techref/index.md

@@ -14,5 +14,6 @@ fonts.md
 text_formatting.md
 patterns.md
 encodings.md
+justification_codes.md
 environment_variables.md
 ```

doc/techref/justification_codes.md

@@ -0,0 +1,23 @@
+Justification codes
+===================
+
+To adjust the position of plot embellishments, such as scalbars, directional roses,
+colorbars, legends, and images, user can adjust the *reference* and *anchor* points.
+
+Pass to `position` parameter and if already implemented `justify`.
+
+Reference point inside / outside of the map bounding box **j** (lower-case) / **J**
+(upper-case), respectively.
+
+Anchor point **+j**.
+
+For both, specify a two-character (order independent) code. Choose from
+
+- Vertical: **T**\(op), **M**\(iddle), **B**\(ottom)
+- Horizontal: **L**\(eft), **C**\(entre), **R**\(ight)
+
+Besides **j** / **J**, the reference point can be set based on
+
+- **g**: Map coordinates as *longitude*/*latitude*
+- **n**: Normalized bounding box coordinates as *nx*/*ny*
+- **x**: Plot coordinates as *x*/*y*