Update libmodbus.txt

Author: zwivhuya13

doc/libmodbus.txt

@@ -33,13 +33,13 @@ library.
 
 Contexts
 ~~~~~~~~
-The Modbus protocol contains many variants (eg. serial RTU or Ehternet TCP), to
+The Modbus protocol contains many variants (eg. serial RTU or Ethernet TCP), to
 ease the implementation of a variant, the library was designed to use a backend
 for each variant. The backends are also a convenient way to fulfill other
 requirements (eg. real-time operations). Each backend offers a specific function
 to create a new 'modbus_t' context. The 'modbus_t' context is an opaque
 structure containing all necessary information to establish a connection with
-others Modbus devices according to the selected variant.
+other Modbus devices according to the selected variant.
 
 You can choose the best context for your needs among: