Lasem 0.5.2

This is a development release:

• viewer: new simple mathml and svg viewer (@mjakeman)
• itex2mml: update to 1.6.1 (@EmmanuelP)
• build: switch to meson (@EmmanuelP)
• build: deprecation warning fixes (@EmmanuelP)
• documentation: port API doc to gi-docgen (@EmmanuelP)
• ci: linux pipeline, valgrind checks, publication of aravis test suite rendering (@EmmanuelP)