Clean up the AppCompat Lint module and its demo

* Always use LINT_API_LATEST version
* Mark UnusedResources and IconMissingDensityFolder to be ignored so
    that we have a clean report in the demo module
* Don't use ?colorPrimary since it triggers an MDC Lint rule

Test: ./gradlew :lint-demo:lint-demo-appcompat:lint
Change-Id: Ie9d8760bdfe52ddbbec7c9d5f9f5e3a2bde43ec3
diff --git a/lint-demos/lint-demo-appcompat/lint.xml b/lint-demos/lint-demo-appcompat/lint.xml
new file mode 100644
index 0000000..c1fddef
--- /dev/null
+++ b/lint-demos/lint-demo-appcompat/lint.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<lint>
+    <issue id="LintBaseline" severity="ignore">
+        <ignore regexp=".* filtered out because .* listed in the baseline file.*"/>
+    </issue>
+    <!-- Ignore all warnings for unused resources since this is not a real app. -->
+    <issue id="UnusedResources" severity="ignore" />
+    <!-- Ignore all warnings for missing icon density folders since this is not a real app. -->
+    <issue id="IconMissingDensityFolder" severity="ignore" />
+    <!-- Ignore all warnings for missing content description since this is not a real app. -->
+    <issue id="ContentDescription" severity="ignore" />
+</lint>