Created SC2296 (markdown)

SC2296.md

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+## Parameter expansions can't start with {. Double check syntax.
+
+(or any other character)
+
+### Problematic code:
+
+```sh
+echo "Hello ${{name}"
+```
+
+### Correct code:
+
+```sh
+echo "Hello ${name}"
+```
+
+### Rationale:
+
+ShellCheck found a parameter expansion `${something}` that starts with an invalid character. In the example, this was caused by accidentally duplicating the `{` in `${{name}`.
+
+Double check the syntax of what you're trying to do.
+
+### Exceptions:
+
+Some Zsh specific parameter expansions like `${(q)value}` trigger this warning, but ShellCheck does not support Zsh.
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!