Fix Svelte compiler warnings

[davidroeca]

There are a number of compiler warnings that pop up when importing svelma in a svelte component with the latest version of svelte. One such warning was mentioned here

Here were the ones that I saw:

WARNING in ./node_modules/svelma/src/components/Dialog/Dialog.svelte
Module Warning (from ./node_modules/svelte-loader-hot/index.js):
Dialog has unused export property 'promise'. If it is for external reference only, please consider using `export const promise` (87:13)
85:   // export let showClose = true
86:   let resolve
87:   export let promise = new Promise((fulfil) => (resolve = fulfil))
                 ^
88:
89:   // TODO: programmatic subcomponents
 @ ./node_modules/svelma/src/components/Dialog/index.js 1:0-36 6:21-27 35:0-6 36:0-6 37:0-6 39:15-21
 @ ./node_modules/svelma/src/index.js

WARNING in ./node_modules/svelma/src/components/Dialog/Dialog.svelte
Module Warning (from ./node_modules/svelte-loader-hot/index.js):
Dialog has unused export property 'subComponent'. If it is for external reference only, please consider using `export const subComponent` (90:13)
88:
89:   // TODO: programmatic subcomponents
90:   export let subComponent = null
                 ^
91:   export let appendToBody = true
92:
 @ ./node_modules/svelma/src/components/Dialog/index.js 1:0-36 6:21-27 35:0-6 36:0-6 37:0-6 39:15-21
 @ ./node_modules/svelma/src/index.js

WARNING in ./node_modules/svelma/src/components/Message.svelte
Module Warning (from ./node_modules/svelte-loader-hot/index.js):
Message has unused export property 'ariaCloseLabel'. If it is for external reference only, please consider using `export const ariaCloseLabel` (14:13)
12:   export let size = ''
13:   export let iconSize = ''
14:   export let ariaCloseLabel = 'delete'
                 ^
15:
16:   let icon
 @ ./node_modules/svelma/src/index.js 8:0-49 17:0-33:1 42:2-9

WARNING in ./node_modules/svelma/src/components/Modal/Modal.svelte
Module Warning (from ./node_modules/svelte-loader-hot/index.js):
Modal has unused export property 'subComponent'. If it is for external reference only, please consider using `export const subComponent` (10:13)
 8:   export let size = ''
 9:   export let showClose = true
10:   export let subComponent = null
                 ^
11:   export let onBody = true
12:
 @ ./node_modules/svelma/src/components/Modal/index.js 1:0-34 3:0-5 5:15-20 8:20-25
 @ ./node_modules/svelma/src/index.js

This PR simply aims to fix them.

[davidroeca]

@abbychau is this PR still necessary? Looks like the only changes are formatting-related

[abbychau]

@davidroeca
I think they are not needed. I have updated the project with a new Svelte Loader.
Thank you.