Move pages under tldr, lint run.sh, update docs

tldr/linux/avifenc

@@ -0,0 +1,17 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# avifenc
+
+> AV1 Image File Format (AVIF) encoder.
+> More information: <https://aomediacodec.github.io/av1-avif/>.
+
+- Convert a specific PNG image to AVIF:
+
+`avifenc {{path/to/input.png}} {{path/to/output.avif}}`
+
+- Encode with a specific speed (6=default, 0=slowest and 10=fastest):
+
+`avifenc --speed {{2}} {{path/to/input.png}} {{path/to/output.avif}}`