Add syntax support for Ada

Add submodule with sublime syntax.

Add corresponding tests for both Ada (in adb/ads) and for the companion tool
gpr.

fixes #1300

Signed-off-by: Marc Poulhiès <dkm@kataplop.net>

.gitmodules

@@ -244,3 +244,6 @@
 	url = https://github.com/victor-gp/cmd-help-sublime-syntax.git
 	branch = main
 	shallow = true
+[submodule "assets/syntaxes/02_Extra/Ada"]
+	path = assets/syntaxes/02_Extra/Ada
+	url = https://github.com/wiremoons/ada-sublime-syntax