Created SC2290 (markdown)

SC2290.md

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+## Remove spaces around = to assign.
+
+### Problematic code:
+
+```sh
+export LC_ALL = "POSIX"
+```
+
+### Correct code:
+
+```sh
+export LC_ALL="POSIX"
+```
+
+### Rationale:
+
+Parameters to `export`, `declare`, `local`, `typeset` and `readonly` may not have spaces around the `=` or `+=` operator. This is the same as for regular variable assignments:
+
+    export var = value   # Invalid: spaces around =
+    export var =value    # Invalid: space before =
+    export var= value    # Invalid: space after =
+    export var=value     # Valid
+ 
+
+### Exceptions:
+
+None
+
+### Related resources:
+
+* Help by adding links to BashFAQ, StackOverflow, man pages, POSIX, etc!