Use Ructe (#327)

All the template are now compiled at compile-time with the `ructe` crate.

I preferred to use it instead of askama because it allows more complex Rust expressions, where askama only supports a small subset of expressions and doesn't allow them everywhere (for instance, `{{ macro!() | filter }}` would result in a parsing error).

The diff is quite huge, but there is normally no changes in functionality.

Fixes #161 and unblocks #110 and #273

.editorconfig

@@ -5,10 +5,10 @@ end_of_line = lf
 insert_final_newline = true
 trim_trailing_whitespace = true
 
-[*.{js,rs,css,tera}]
+[*.{js,rs,css,tera,html}]
 charset = utf-8
 
-[*.{rs,tera,css}]
+[*.{rs,tera,css,html}]
 indent_style = space
 indent_size = 4