TGA: Support for TGA specification 2.0

Adds TGA 2.0 compliance:
- Support for Extension Area, Developer Area and Footer (metadata support)
- Support for 15-bit and 16-bit per pixel images (both RGB and Indexed)
- Full support for rotation on reading (we cannot use Qt transformations because only a subset is part of the TGA specification)
- When writing you can choose the supported version (subType)
- Improved writing speed (approximately 10 times) and removed whole image conversions (significant memory savings)

It pass the [TrueVision TGA 2.0 conformance suite](https://github.com/zigimg/test-suite/tree/master/fixtures/tga).

Test changes:
- Read test: added ability to skip a specific test on sequential devices (via JSON behavior file)
- Write test: added the ability to set the subType when writing (via JSON properties file)

Closes #37

README.md

@@ -56,11 +56,17 @@ submit the plugin directly to the Qt Project.
 To be accepted, contributions must:
 - Contain the test images needed to verify that the changes work correctly.
 - Pass the tests successfully.
+- Use Qt logging categories for Debug messages.
 
 For more info about tests, see also [Autotests README](autotests/README.md).
 
 ## Duplicated Plugins
 
+> [!important]
+> To ensure you are using the correct plugin, the unwanted one should be 
+renamed or deleted. If several plugins support the same capability, Qt will 
+select one arbitrarily.
+
 ### The TGA plugin
 
 The TGA plugin supports more formats than Qt's own TGA plugin;
@@ -340,10 +346,6 @@ The plugin supports the following image data:
 - FOR4 CIMG (Maya Image File Format): It supports 24/48-bit RGB and 32/64-bit 
   RGBA images.
 
-The plugin does not load images with non-standard SHAM/CTBL chunks due to the
-lack of clear specifications.
-
-
 ### The JP2 plugin
 
 **This plugin can be disabled by setting `KIMAGEFORMATS_JP2` to `OFF` 
@@ -426,6 +428,25 @@ selectively change the conversion (see also [raw_p.h](./src/imageformats/raw_p.h
 
 The default setting tries to balance quality and conversion speed.
 
+### The TGA plugin
+
+TGA plugin supports both version 1 and version 2 of TGA files. When writing,
+it is possible to force which version to use by setting the following subtypes:
+- `TGAv1`: force TGA v1.0. No metadata.
+- `TGAv2` (default): force TGA v2.0 (strict). Adds the TGA Extension Area.
+- `TGAv2E`: force TGA v2.0 (enhanced). Same as TGA v2.0 (strict) but with the 
+  addition of the TGA v2.0 Developer Area with info like, for e.g., Exif data, 
+  XMP packet and the ICC profile.
+
+They are all TGA specs compliant. While for versions 1 and 2 (strict) it is 
+possible to decode all the information with the TGA specification alone, for 
+version 2 (enhanced) it is necessary to know how the additional data is
+encoded.
+
+The following defines can be defined in cmake to modify the behavior of the 
+plugin:
+- `TGA_V2E_AS_DEFAULT`: change the default version of the plugin to `TGAv2E`.
+
 ### The XCF plugin
 
 XCF support has the following limitations: