feat(*): switched to spdlog for logging and organized headers (#1183)

* feat: updated PKGBUILD description
* feat: updated workflow syntax and dependencies
* feat: switched logging to spdlog
* chore: adjusted library defaults
* ci: fixed spdlog format string issues
* docs: fixed docs for libvideo2x functions
* feat: organized header files
* fix: fixed header installation directory
* feat: link spdlog statically if compiled from source
* feat: adjusted libvideo2x log level enum names
* feat: added version.h header

Signed-off-by: k4yt3x <i@k4yt3x.com>

include/libvideo2x/encoder.h

@@ -0,0 +1,33 @@
+#ifndef ENCODER_H
+#define ENCODER_H
+
+extern "C" {
+#include <libavcodec/avcodec.h>
+#include <libavformat/avformat.h>
+#include <libavutil/opt.h>
+}
+
+#include "libvideo2x.h"
+
+int init_encoder(
+    AVBufferRef *hw_ctx,
+    const char *output_filename,
+    AVFormatContext *ifmt_ctx,
+    AVFormatContext **ofmt_ctx,
+    AVCodecContext **enc_ctx,
+    AVCodecContext *dec_ctx,
+    EncoderConfig *encoder_config,
+    int video_stream_index,
+    int **stream_mapping
+);
+
+int encode_and_write_frame(
+    AVFrame *frame,
+    AVCodecContext *enc_ctx,
+    AVFormatContext *ofmt_ctx,
+    int video_stream_index
+);
+
+int flush_encoder(AVCodecContext *enc_ctx, AVFormatContext *ofmt_ctx);
+
+#endif  // ENCODER_H