Create README.md

Author: mug1wara26

server/src/rules/README.md

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+# Rules
+Documentation for all diagnostics sent back to the client.
+## Warnings
+
+### [No unused variables](ast.ts)
+**Error message**: `Unused name`
+Flags variables that are declared but not used within the code.
+```javascript
+const pi = 3.14;
+display(5*5*3.14);
+```
+The variable `pi` should have a warning.
+
+## Errors
+
+### [Missing semicolon](ast.ts)  
+Identifies statements that are missing semicolons.
+```javascript
+const x = 1;
+```
+The line ending should have an error.
+
+### [Trailing comma](ast.ts)  
+Identifies expressions that have trailing commas.
+```javascript
+const x = [1,2,3,];
+```
+The comma after `3` should have an error.
+
+### [No namespace/default imports](ast.ts)  
+**Error message**: `Only normal imports are allowed`
+Bans namespace and default imports.
+```javascript
+import * as rune from "rune";
+import black from "rune";
+```
+Both lines will throw an error around the identifier.
+
+### [Unexpected token in function parameters](ast.ts) 
+**Error message**: `Unexpected token`
+Only allows identifiers as function parameters
+```javascript
+function foo(a+b) {}
+```
+`a+b` will throw an error.
+
+### [Redeclaration of variables](ast.ts)  
+**Error message**: `Identifier '${name}' has already been declared`
+Bans redeclaration of names in the same scope
+```javascript
+let x = 1;
+let x = 2;
+```
+The second `x` will throw an error.
+
+### [No array expressions](rules/arrayExpression.ts)  
+**Error message**: `Array expressions are not allowed`
+Bans array expressions before Source 3
+```javascript
+const x = [1,2,3];
+```
+The array `[1,2,3];` will throw an error.
+
+### [No empty elements](rules/arrayExpression.ts)
+**Error message**: `No holes are allowed in array literals`
+Bans empty elements in array expressions
+```javascript
+[1,,3];
+```
+The array `[1,,3]` will throw an error.
+
+### [Constant reassignment](rules/assignmentExpression.ts)
+**Error message**: `Cannot assign new value to constant ${name}`
+Bans reassignment to constant variable
+```javascript
+const x = 1;
+x = 2;
+```
+The second `x` will throw an error
+
+### [Incomplete binary expression](rules/binaryExpression.ts)
+**Error message**: `Incomplete binary expression`
+Detects when a binary expression is missing a left/right node
+```javascript
+10 + ;
+5 === ;
+```
+Both lines will throw an error
+
+### [Force strict equality](rules/binaryExpression.ts)
+**Error message**: `Use ===/!== instead of ==/!=`
+Bans the use of loose equality checks `==` and `!=`
+```javascript
+true == 1;
+```
+
+### [Disallowed operators](rules/binaryExpression.ts)
+**Error message**: `${operator} is not allowed`
+Only permitted operators defined in Source is allowed. Binary operators like `^` or `instanceof` is banned.
+```javascript
+100^5;
+```
+The expression `100^5` will throw an error.
+
+### [Only string or number in equality checks](rules/binaryExpression.ts)
+**Error message**: `Expected string or number on left/right hand side of operation, got ${type}`
+Before Source 3, only strings or numbers can be in equality checks
+```javascript
+true === 1; // Expected string or number on left hand side of operation, got boolean
+true === (1 === 1); // Expected string or number on left hand side of operation, got boolean
+(1 === 1) === undefined; // Expected string or number on right hand side of operation, got undefined
+"string" === 1; // Expected string on left hand side of operation, got number
+```
+Errors are shown in the comments.
+
+### [No break statements](rules/breakStatement.ts)
+**Error message**: `Break statements are not allowed;`
+No break statements before Source 3
+```javascript
+break;
+```
+`break` will throw an error.
+
+### [Calling a non function](rules/callExpression.ts)  
+**Error message**: `${name} is not a function`
+Cannot call identifiers that are not a function
+```javascript
+const x = 1;
+x();
+let y = 1;
+y()
+```
+The function application on `x` will throw an error, however the function application on `y` will not, as y 
+can be reassigned, hence it will be a runtime error.
+
+### [Not enough parameters](rules/callExpression.ts)  
+**Error message**: `Expected ${num_args} or more arguments, but got ${num_supplied_args}`
+Detects when a function application has not enough parameters.
+```javascript
+display();
+```
+The call to `display` needs at least 1 element.
+
+```javascript
+```