Added a couple of interesting and easy features with a few code

[pimoGit]

VIDEO_BROWSER:

• added a search bar label;
• parametrized initial term in the index and passed as props in the search bar as a placeholder;

BOOK_LIST:

• added selected book feature;
• changed a component from class to functional;

WEATHER:

• fetchPostObject in vanilla js, instead of lodash;

BOOK_LIST:

• fectch_post only if necessary;
• customized the content field in a textarea;
• take the content (of the content field) formatting.

ALL: added some comments.