Content for P4test Backend

Signed-off-by: Adarsh <Adarshbunny293@gmail.com>

backends/p4test/README.md

@@ -1,3 +1,39 @@
 # P4test Backend
 
-This is a "fake" backend, whose sole purpose is to test the P4-16 front-end.
+The P4test Backend is a tool designed for testing and debugging P4
+programs. It supports both the P4_14 and P4_16 standards and can
+translate P4 code from one version to another. Additionally, it
+provides a syntax checker for P4 code, enabling the verification of 
+the correctness of your P4 programs. It supports both the P4_14 and 
+P4_16 standards and can translate P4 code from one version to another.
+
+## Auto-translate P4_14 source to P4_16 source:
+You can automatically translate a P4_14 program to a P4_16 program
+using the following command:
+```bash
+p4test --std p4-14 my-p4-14-prog.p4 --pp auto-translated-p4-16-prog.p4
+```
+
+This command takes the P4_14 program (my-p4-14-prog.p4) and generates
+a corresponding P4_16 program (auto-translated-p4-16-prog.p4).
+
+
+## Check syntax of P4_16 or P4_14 source code
+The P4test Backend can check the syntax of P4 programs without being
+restricted by any specific compiler back end. This is useful for
+ensuring that your P4 code is syntactically correct.
+
+For P4_16 code: 
+```bash
+p4test my-p4-16-prog.p4
+```
+
+For P4_14 code: 
+```bash
+p4test --std p4-14 my-p4-14-prog.p4
+```
+
+These commands will output error and/or warning messages if there 
+are any issues with the syntax of your P4 code, enabling you to
+verify the correctness of your P4 programs, due to that it is 
+possible to verify the correctness of your P4 programs.

docs/doxygen/p4c_layout.xml

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       <tab type="modulelist" visible="yes" title="" intro=""/>
       <tab type="modulemembers" visible="yes" title="" intro=""/>
     </tab>
-    <tab type="namespaces" visible="no" title="">
+    <tab type="namespaces" visible="yes" title="">
       <tab type="namespacelist" visible="yes" title="" intro=""/>
       <tab type="namespacemembers" visible="yes" title="" intro=""/>
     </tab>
@@ -21,7 +21,7 @@
       <tab type="interfaceindex" visible="$ALPHABETICAL_INDEX" title=""/>
       <tab type="interfacehierarchy" visible="yes" title="" intro=""/>
     </tab>
-    <tab type="classes" visible="no" title="">
+    <tab type="classes" visible="yes" title="">
       <tab type="classlist" visible="yes" title="" intro=""/>
       <tab type="classindex" visible="$ALPHABETICAL_INDEX" title=""/>
       <tab type="hierarchy" visible="yes" title="" intro=""/>