Add Endian.HC functions from minexew's SnailNet library

Endian.HC

@@ -0,0 +1,15 @@
+U16 htons(U16 h) {
+    return ((h >> 8) | (h << 8)) & 0xffff;
+}
+
+U16 ntohs(U16 h) {
+    return ((h >> 8) | (h << 8)) & 0xffff;
+}
+
+U32 htonl(U32 h) {
+    return ((h >> 24) | ((h & 0x00ff0000) >> 8) | ((h & 0x0000ff00) << 8) | (h << 24)) & 0xffffffff;
+}
+
+U32 ntohl(U32 h) {
+    return ((h >> 24) | ((h & 0x00ff0000) >> 8) | ((h & 0x0000ff00) << 8) | (h << 24)) & 0xffffffff;
+}

FilePNG.HC

@@ -234,7 +234,7 @@ public I64 PNGWrite(U8 *filename,CDC *dc,I64 bits=4)
   FileWrite(filename,png,size);
   Free(png);
   return size;
-}
+}
 
 #help_index "Graphics/PNG Files;Graphics/Scrn"
 public I64 PNGScrnCapture(U8 *filename,I64 bits=4,Bool include_zoom=TRUE)

README.md

@@ -2,3 +2,10 @@
 PNG support for TempleOS
 
 ![FilePNG](https://raw.githubusercontent.com/tramplersheikhs/filepng/master/example.png "FilePNG")
+
+`#include "Endian"` (if needed)
+
+`#include "FilePNG"`
+
+
+`PNGScrnCapture;` and `PNGWrite("filename.png");` functions are present.