fix(a11y): add keyboard support to no-signatures area and translatable action labels

- Add role='button', tabindex=0 and keydown handlers to .no-signatures
  div so keyboard users can activate it to start editing
- Use translatable t('libresign', 'Delete {type}') and t('libresign',
  'Edit {type}') in action button labels
- Pass :alt with 'Current {type}' to PreviewSignature for context

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

src/views/Account/partials/Signature.vue

@@ -13,21 +13,32 @@
 					<template #icon>
 						<NcIconSvgWrapper :path="mdiDelete" :size="20" />
 					</template>
+					<!-- TRANSLATORS {type} is the kind of signature element being deleted, e.g. "signature" or "initial" -->
+					{{ t('libresign', 'Delete {type}', { type }) }}
 				</NcActionButton>
 				<NcActionButton @click="edit">
 					<template #icon>
 						<NcIconSvgWrapper :path="mdiDraw" :size="20" />
 					</template>
+					<!-- TRANSLATORS {type} is the kind of signature element being edited, e.g. "signature" or "initial" -->
+					{{ t('libresign', 'Edit {type}', { type }) }}
 				</NcActionButton>
 			</NcActions>
 		</header>
 
 		<div v-if="hasSignature">
 			<PreviewSignature :src="imgSrc"
 				:sign-request-uuid="signatureElementsStore.signRequestUuid"
+				:alt="t('libresign', 'Current {type}', { type })"
 				@loaded="signatureLoaded" />
 		</div>
-		<div v-else class="no-signatures" @click="edit">
+		<div v-else
+			class="no-signatures"
+			role="button"
+			tabindex="0"
+			@click="edit"
+			@keydown.enter.prevent="edit"
+			@keydown.space.prevent="edit">
 			<slot name="no-signatures" />
 		</div>