Credit syntax definition and theme authors with new --acknowledgements option (#1971)

The text that is printed is generated when building assets, by analyzing LICENSE
and NOTICE files that comes with syntaxes and themes.

We take this opportunity to also add a NOTICE file as defined by Apache License 2.0.

src/assets.rs

@@ -55,6 +55,9 @@ pub(crate) const COMPRESS_THEMES: bool = false;
 /// performance due to lazy-loading
 pub(crate) const COMPRESS_LAZY_THEMES: bool = true;
 
+/// Compress for size of ~10 kB instead of ~120 kB
+pub(crate) const COMPRESS_ACKNOWLEDGEMENTS: bool = true;
+
 impl HighlightingAssets {
     fn new(serialized_syntax_set: SerializedSyntaxSet, theme_set: LazyThemeSet) -> Self {
         HighlightingAssets {
@@ -305,6 +308,13 @@ pub(crate) fn get_integrated_themeset() -> LazyThemeSet {
     from_binary(include_bytes!("../assets/themes.bin"), COMPRESS_THEMES)
 }
 
+pub fn get_acknowledgements() -> String {
+    from_binary(
+        include_bytes!("../assets/acknowledgements.bin"),
+        COMPRESS_ACKNOWLEDGEMENTS,
+    )
+}
+
 pub(crate) fn from_binary<T: serde::de::DeserializeOwned>(v: &[u8], compressed: bool) -> T {
     asset_from_contents(v, "n/a", compressed)
         .expect("data integrated in binary is never faulty, but make sure `compressed` is in sync!")