feat: new mf_readfile macro (and test)

tests/base/mf_readfile.test.sas

@@ -0,0 +1,29 @@
+/**
+  @file
+  @brief Testing mf_readfile.sas macro
+
+  <h4> SAS Macros </h4>
+  @li mf_readfile.sas
+  @li mp_assert.sas
+
+**/
+
+%let f=&sasjswork/myfile.txt;
+
+%mf_writefile(&f,l1=some content,l2=more content)
+data _null_;
+  infile "&f";
+  input;
+  putlog _infile_;
+run;
+
+%mp_assert(
+  iftrue=(&syscc=0),
+  desc=Check code ran without errors,
+  outds=work.test_results
+)
+%mp_assert(
+  iftrue=(&f=some content),
+  desc=Checking first line was ingested successfully,
+  outds=work.test_results
+)