Here is a quick how-to outlining the process to create custom inkscape SVG filters to style text. The tutorial covers the procedure to create a filter for text with a shadow, slightly inset text and raised, super glossy text. The tutorial also has a downloadable SVG so you can open up the image in Inkscape and play with the filters yourself.
We have posted many tutorials in the past covering how to achieve a shiny effect in inkscape. A newbie inkscaper should be able to follow the detailed directions to create a shiny Donate button as a first inkscape project.