Add dedicated README and borrow linux .gitignore

.gitignore

@@ -104,3 +104,41 @@ all.config
 
 # Kdevelop4
 *.kdev4
+
+# Perf specific
+PERF-CFLAGS
+PERF-GUI-VARS
+PERF-VERSION-FILE
+FEATURE-DUMP
+perf
+perf-read-vdso32
+perf-read-vdsox32
+perf-help
+perf-record
+perf-report
+perf-stat
+perf-top
+perf*.1
+perf*.xml
+perf*.html
+common-cmds.h
+perf.data
+perf.data.old
+output.svg
+perf-archive
+perf-with-kcore
+tags
+TAGS
+cscope*
+config.mak
+config.mak.autogen
+*-bison.*
+*-flex.*
+*.pyc
+*.pyo
+.config-detected
+util/intel-pt-decoder/inat-tables.c
+arch/*/include/generated/
+trace/beauty/generated/
+pmu-events/pmu-events.c
+pmu-events/jevents