Documentation improvements.

v1.0.8

Merge branch 'main' of https://github.com/veelo/gettext into main

New Context and Comment API

Previously, context and notes to the translator were supplied as an associate array literal:

tr!("Review the draft.", [Tr.context: "nautical",
                          Tr.note: `Nautical term! "Draft" = how deep the bottom` ~
                                   `of the ship is below the water level.`]);

Now, the preferred way is this:

tr!("Review the draft.", Context("nautical"),
                         Comment(`Nautical term! "Draft" = how deep the bottom` ~
                                 `of the ship is below the water level.`));

The previous form is still supported, but intentionally not documented.

Context and comments on plural forms.

• Support plural forms with context differentiation and comments to the translator.
• Improvements to the documentation.

gettext:todo robustness

• Increase the robustness of the scanner for untranslated strings gettext:todo.
• Add documentation for justifying translated strings.

Bug fix.

Don't throw on non-format strings containing %.