Migration of jsx files to tsx 1 (#848)

In this PR I have changed some of the jsx files to tsx file.
I'm starting off with the "leafs" so that migration of the rest will be
easier, hopefully.

What I'm basically doing is taking a jsx file, copy paste it into:
https://mskelton.dev/ratchet

And after that I'm fixing the types as needed.
It's not a very long process.

Hopefully more PRs will follow and this will be over soon.
I don't plan to migrate the storybook as I generally don't understand
why is it useful, I'll open an issue to see if anyone thinks
differently.

src/components/Fieldset.tsx

@@ -0,0 +1,66 @@
+import React, { ReactElement } from 'react'
+import FieldDocLabel from './FieldDocLabel'
+import Doc from './Doc'
+
+type FieldsetProps = {
+  label?: string,
+  fieldSpec?: { doc?: string },
+  action?: ReactElement,
+};
+
+type FieldsetState = {
+  showDoc: boolean
+};
+
+let IDX = 0;
+
+export default class Fieldset extends React.Component<FieldsetProps, FieldsetState> {
+  _labelId: string;
+
+  constructor (props: FieldsetProps) {
+    super(props);
+    this._labelId = `fieldset_label_${(IDX++)}`;
+    this.state = {
+      showDoc: false,
+    }
+  }
+
+  onToggleDoc = (val: boolean) => {
+    this.setState({
+      showDoc: val
+    });
+  }
+
+  render () {
+    return <div className="maputnik-input-block" role="group" aria-labelledby={this._labelId}>
+      {this.props.fieldSpec &&
+        <div className="maputnik-input-block-label">
+          <FieldDocLabel
+            label={this.props.label}
+            onToggleDoc={this.onToggleDoc}
+            fieldSpec={this.props.fieldSpec}
+          />
+        </div>
+      }
+      {!this.props.fieldSpec &&
+        <div className="maputnik-input-block-label">
+          {this.props.label}
+        </div>
+      }
+      <div className="maputnik-input-block-action">
+        {this.props.action}
+      </div>
+      <div className="maputnik-input-block-content">
+        {this.props.children}
+      </div>
+      {this.props.fieldSpec &&
+        <div
+          className="maputnik-doc-inline"
+          style={{display: this.state.showDoc ? '' : 'none'}}
+        >
+          <Doc fieldSpec={this.props.fieldSpec} />
+        </div>
+      }
+    </div>
+  }
+}