update read_nexus readme

pynxtools/nexus/README.md

@@ -1,3 +1,6 @@
+# Debugger and
+
+
 This utility outputs a debug log for a given NeXus file by annotating the data and
 metadata entries with the schema definitions from the respective NeXus base classes
 and application definitions to which the file refers to.
@@ -23,6 +26,11 @@ read_nexus [Options] <path_to_nexus_file>
 
 ```
 
+The following example dataset can be used to test the `read_nexus` module: `tests/data/nexus/201805_WSe2_arpes.nxs`.
+This is an angular-resolved photoelectron spectroscopy (ARPES) dataset and it is formatted according to
+the [NXarpes application definition of NeXus](https://manual.nexusformat.org/classes/applications/NXarpes.html#nxarpes).
+
+## Using a different set of NeXus definitions
 _The environmental variable called "NEXUS_DEF_PATH" can be set to
 a directory, which contains the NeXus definitions as XML files. If this environmental
 variable is not defined, the module will use the definitions in its bundle._
@@ -33,12 +41,8 @@ An environmental variable can be set as follows:
 export 'NEXUS_DEF_PATH'=<folder_path_that_contains_nexus_defs>
 ```
 
-Following example dataset can be used to test `read_nexus` module `tests/data/nexus/201805_WSe2_arpes.nxs`.
-This is an angular-resolved photoelectron spectroscopy (ARPES) dataset and it is formatted according to
-the [NXarpes application definition of NeXus](https://manual.nexusformat.org/classes/applications/NXarpes.html#nxarpes).
-
-
-A note to Windows users: if you run `read_nexus` from `git bash`, you need to set the environmental variable
+## A note to Windows users
+If you run `read_nexus` from `git bash`, you need to set the environmental variable
 `MSYS_NO_PATHCONV` to avoid the [path translation in Windows Git MSys](https://stackoverflow.com/questions/7250130/how-to-stop-mingw-and-msys-from-mangling-path-names-given-at-the-command-line#34386471).
 The easiest way is to prefix the `read_nexus` call with `MSYS_NO_PATHCONV=1`: