Docs: document E052, E147

Author: strager

docs/errors/E052.md

@@ -0,0 +1,38 @@
+# E052: unexpected '#'
+
+```config-for-examples
+{
+  "globals": {
+    "encrypt": true,
+    "sendMessage": true,
+
+    "synchronous": true,
+    "blocking": true
+  }
+}
+```
+
+In JavaScript, `#` is used for shebangs at the beginning of a file (e.g.
+`#!/usr/bin/env node`) and private properties. (`#` does not start a comment.)
+It is an error to use `#` anywhere else:
+
+    class Auth {
+      #password;
+
+      authenticate() {
+        # synchronous (blocking)
+        sendMessage(encrypt(this.# password));
+      }
+    }
+
+To fix this error, write the property's name after `#`, and use `//` for line
+comments:
+
+    class Auth {
+      #password;
+
+      authenticate() {
+        // synchronous (blocking)
+        sendMessage(encrypt(this.#password));
+      }
+    }

docs/errors/E147.md

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+# E147: unexpected identifier in expression; missing operator before
+
+```config-for-examples
+{
+  "globals": {
+    "add": true,
+    "dos": true,
+    "two": true
+  }
+}
+```
+
+It is an error to write two variable names without an operator in between:
+
+    const quatro = (dos dos);
+    const four = add(two two);
+
+To fix this error, remove one of the variables, or add an operator:
+
+    const quatro = (dos + dos);
+    const four = add(two, two);