fix regex to only be true for source maps

AssemblyScript compiler can generate lines that contain the `@` symbol but have nothing to do with the source mapping (e.g., '000287d: 6e67 2e55 5446 382e 656e 636f 6465 4076  ng.UTF8.encode@v') which causes `extractLineInfo` to fail on those lines.
This commit modifies the regex to only be true for lines that start with `@ {` which ensures that `extractLineInfo` is applied to real source map lines.

src/CompilerBridges/WASMCompilerBridge.ts

@@ -48,7 +48,7 @@ function createLineInfoPairs(lines: string[]): LineInfoPairs[] { // TODO update
     let lastLineInfo = undefined;
     for (let i = 0; i < lines.length; i++) {
         const line = lines[i];
-        const newLine = line.match(/@/);
+        const newLine = line.match(/@ {/);
         if (newLine) {
             lastLineInfo = extractLineInfo(line);
             continue;