Merge P4C Overview with P4C root README

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

README.md

@@ -41,6 +41,8 @@ P4C is modular; it provides a standard frontend and midend which can be combined
 with a target-specific backend to create a complete P4 compiler. The goal is to
 make adding new backends easy.
 
+\include{doc} "../docs/doxygen/01_overview.md"
+
 The code contains seven sample backends:
 * p4c-bm2-ss: can be used to target the P4 `simple_switch` written using
   the [BMv2 behavioral model](https://github.com/p4lang/behavioral-model),

docs/doxygen/doxygen.cfg

@@ -941,7 +941,6 @@ WARN_LOGFILE           = p4c-doxygen-warn.log
 
 INPUT                 = ../../docs/README.md \
                         ../../README.md \ 
-                        ../../docs/doxygen/01_overview.md \
                         ../../docs/doxygen \
                         ../../frontends \
                         ../../midend \
@@ -1036,6 +1035,7 @@ EXCLUDE                = ../../frontends/p4/README.md \
                          ../../backends/p4tools/modules/testgen/targets/bmv2/test/README.md \
                          ../../backends/ubpf/docs/EXAMPLES.md \
                          ../../backends/ubpf/tests/README.md \
+                         ../../docs/doxygen/01_overview.md \
 
 # The EXCLUDE_SYMLINKS tag can be used to select whether or not files or
 # directories that are symbolic links (a Unix file system feature) are excluded