add <label> tag for search bar
add <label> tag for search bar


Former-commit-id: e58a42d092f8cf0412431ea6198581f77850e445 [formerly 32dd43098acdcc702442915b0f8a6469b57c20c1]
Former-commit-id: 6eb81d655f9d56c2bcd75a2f06170d7704d73cf0
LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io,LibraryCarpentry/librarycarpentry.github.io