page.js: Change `innerHTML` to `textContent`firefox-webextension

Fix this warning received during validation while signing the extension
with Mozilla:

    Unsafe assignment to innerHTML
    Warning: Due to both security and performance concerns, this may not
    be set using dynamic values which have not been adequately
    sanitized. This can lead to security issues or fairly serious
    performance degradation.

1 files changed, 1 insertions, 1 deletions

diff --git a/page.js b/page.js
index fa2f0b0..f616b09 100644
--- a/page.js
+++ b/page.js
@@ -1,3 +1,3 @@
 (function() {
-	document.getElementById('header').innerHTML = generate_file_string();
+	document.getElementById('header').textContent = generate_file_string();
 })();
\ No newline at end of file