Revise building docs and ignore testing tmp files

Signed-off-by: TTFISH <jiongchiyu@gmail.com>

Author: fish98

.gitignore

@@ -93,4 +93,6 @@ test-pdf
 test-ps
 testfilters
 test-analyze
-Test_summary_final.txt
+Test_summary_final.txt
+test.pdf
+test.ps

INSTALL.md

@@ -77,6 +77,11 @@ or
 - libcupsfilters is supported for CUPS from version 2.2.2.
 - For earlier CUPS versions (1.5.x, required since 1.6.x), use cups-filters 1.x.
 
+## Testing
+- For CI testing and build checks, run with:
+```
+make check
+```
 
 ## Installing Required Tools