Use a more realistic texture of the Sun

Current texture of the Sun looks cartoonish and doesn't reflect the real
look of the Sun. It not only has wrong colors, but also wrong granule
sizes and sunspot sizes, locations, and contrast.

The new texture is made from the SDO HMI observations, which
automatically fixes these issues. The texture is a result of stitching
the maps obtained from multiple HMI images, with the equatorial region
containing the sunspots taken from observations from 2025-08-07 to
2025-08-31, while the rest is filled with spotless data of 2019-12-15.
All the source images were considered valid only in the central 60% of
the solar disk, because outside that region the faculae become more
prominent, which is undesired for such a generic texture expected to be
viewed from different angles.

Author: 10110111

CREDITS.md

@@ -277,7 +277,7 @@
 	4.3a Jupiter map created by James Hastings-Trew from Cassini data. "The 
 	     maps are free to download and use as source material or resource
 	     in artwork or rendering (CGI or real time)."
-	4.3b The Sun and Iapetus maps and rings of Uranus 
+	4.3b The Iapetus map and the rings of Uranus
 	     are from Celestia (http://shatters.net/celestia/)
 	     under the GNU General Purpose License, version 2 or any later
 	     version:
@@ -310,6 +310,9 @@
 	     http://maps.jpl.nasa.gov/   see license in section 10.2
 	4.3n Bennu map is created by NASA from OSIRIS-REx spacecraft data. Public domain.
 	     Full size mosaic: https://www.asteroidmission.org/bennu_global_mosaic/
+	4.3o The Sun map was created by Ruslan Kabatsayev from the images taken by SDO HMI.
+	     The map is under the GNU General Public License, version 2 or any later
+	     version.
 	4.4 The fullsky milky way panorama is created by Axel Mellinger,
 	    University of Potsdam, Germany. Further information and more
 	    pictures available from

data/ssystem_major.ini

@@ -1767,7 +1767,7 @@ radius=696000.
 rot_equator_ascending_node=196.13
 rot_obliquity=7.25
 ;rot_periode=654.61
-tex_map=sun.png
+tex_map=sun.webp
 type=star
 rot_pole_ra=286.13
 rot_pole_de=63.87

textures/CMakeLists.txt

@@ -3,6 +3,7 @@
 INSTALL(DIRECTORY ./ DESTINATION ${SDATALOC}/textures
         FILES_MATCHING PATTERN "*.png"
         PATTERN "*.jpg"
+        PATTERN "*.webp"
         PATTERN "CMakeFiles" EXCLUDE )