Add prefix and suffix string trimming functions

This is needed to fix extraneous whitespace issues in image posts

damus/Views/NoteContentView.swift

@@ -346,3 +346,14 @@ struct TruncatedText: View {
         return AttributedString(truncatedAttributedString) + "..."
     }
 }
+
+
+// trim suffix whitespace and newlines
+func trim_suffix(_ str: String) -> String {
+    return str.replacingOccurrences(of: "\\s+$", with: "", options: .regularExpression)
+}
+
+// trim prefix whitespace and newlines
+func trim_prefix(_ str: String) -> String {
+    return str.replacingOccurrences(of: "^\\s+", with: "", options: .regularExpression)
+}

damusTests/damusTests.swift

@@ -40,6 +40,13 @@ class damusTests: XCTestCase {
         XCTAssertEqual(bytes.count, 32)
     }
     
+    func testTrimmingFunctions() {
+        let txt = "   bobs   "
+        
+        XCTAssertEqual(trim_prefix(txt), "bobs   ")
+        XCTAssertEqual(trim_suffix(txt), "   bobs")
+    }
+    
     func testParseMentionWithMarkdown() {
         let md = """
         Testing markdown in damus