Update syntax readme and docs

runtime/syntax/README.md

@@ -1,5 +1,27 @@
 # Syntax Files
 
-Here are highlight's syntax files. If you would like to make a new syntax file, you should first check it
-with the `syntax_checker.go` program. Just place it in this directory and run the program (`go run syntax_checker.go`)
-and it will let you know if there are issues with any of the files in the directory.
+Here are micro's syntax files.
+
+Each yaml file specifies how to detect the filetype based on file extension or headers (first line of the file).
+Then there are patterns and regions linked to highlight groups which tell micro how to highlight that filetype.
+
+Making your own syntax files is very simple. I recommend you check the file after you are finished with the
+[`syntax_checker.go`](./syntax_checker.go) program (located in this directory). Just place your yaml syntax
+file in the current directory and run `go run syntax_checker.go` and it will check every file. If there are no
+errors it will print `No issues!`.
+
+You can read more about how to write syntax files (and colorschemes) in the [colors](../help/colors.md) documentation.
+
+# Legacy '.micro' filetype
+
+Micro used to use the `.micro` filetype for syntax files which is no longer supported. If you have `.micro`
+syntax files that you would like to convert to the new filetype, you can use the [`syntax_converter.go`](./syntax_converter.go) program (also located in this directory):
+
+```
+$ go run syntax_converter.go c.micro > c.yaml
+```
+
+Most the the syntax files here have been converted using that tool.
+
+Note that the tool isn't perfect and though it is unlikely, you may run into some small issues that you will have to fix manually
+(about 4 files from this directory had issues after being converted).