Split integrations and export into ext module

feat: move integrations from lib to ext
feat: move content export from lib to ext
feat: rename affected packages for separate module distribution
chore: update Gradle module wiring
chore: adjust JPMS descriptors and dependencies
docs: update module structure documentation

ext/build.gradle

@@ -0,0 +1,13 @@
+plugins {
+    id 'buildlogic.java-library-conventions'
+    id 'com.palantir.git-version'
+}
+
+group='org.egothor'
+
+dependencies {
+	api 'org.bouncycastle:bcpkix-jdk18on'
+	implementation 'org.apache.commons:commons-imaging'
+	implementation project(':lib')
+	testImplementation 'org.egothor:conflux'
+}