Rename to @sigmacomputing/babel-plugin-lodash and fix module declaration bug

[Pearce-Ropion]

Fork original lodash/babel-plugin-lodash to @sigmacomputing/babel-plugin-lodash

• #261 hasn't seen any kind of acknowledgement from the package authors

Resolves #259

The isModuleDeclaration method was recently deprecated in
babel/babel#15266 which causes deprecation notices akin to the following:

Trace: `isModuleDeclaration` has been deprecated, please migrate to `isImportOrExportDeclaration`.
    at isModuleDeclaration (/path/to/example/node_modules/@babel/types/lib/validators/generated/index.js:3939:11)
    at PluginPass.Program (/path/to/example/node_modules/babel-plugin-example/lib/index.js:102:44)
    at newFn (/path/to/example/node_modules/@babel/traverse/lib/visitors.js:148:21)
    at NodePath._call (/path/to/example/node_modules/@babel/traverse/lib/path/context.js:45:20)
    at NodePath.call (/path/to/example/node_modules/@babel/traverse/lib/path/context.js:35:17)
    at NodePath.visit (/path/to/example/node_modules/@babel/traverse/lib/path/context.js:80:31)
    at TraversalContext.visitQueue (/path/to/example/node_modules/@babel/traverse/lib/context.js:86:16)
    at TraversalContext.visitSingle (/path/to/example/node_modules/@babel/traverse/lib/context.js:65:19)
    at TraversalContext.visit (/path/to/example/node_modules/@babel/traverse/lib/context.js:109:19)
    at traverseNode (/path/to/example/node_modules/@babel/traverse/lib/traverse-node.js:18:17)

According to the migration guide, babel plugins are recommended to replace the method with either isImportOrExportDeclaration in the case where backward compatibility is not essential. Or, if backward compatibility is an issue, a combination of isImportDeclaration and isExportDeclaration. This PR applies the latter.

The recommendation mentioned above can be found in the "Migration guide (for plugin authors)" section of babel/babel#15266.

Relates to #260 – I didn't have permission to update that PR and it hasn't had any movement from the PR author for a while.